Language selection

Search

Patent 1085575 Summary

Third-party information liability

Some of the information on this Web page has been provided by external sources. The Government of Canada is not responsible for the accuracy, reliability or currency of the information supplied by external sources. Users wishing to rely upon this information should consult directly with the source of the information. Content provided by external sources is not subject to official languages, privacy and accessibility requirements.

Claims and Abstract availability

Any discrepancies in the text and image of the Claims and Abstract are due to differing posting times. Text of the Claims and Abstract are posted:

  • At the time the application is open to public inspection;
  • At the time of issue of the patent (grant).
(12) Patent: (11) CA 1085575
(21) Application Number: 321071
(54) English Title: WHEELED PORTABLE TRAILER SUBSTRUCTURE FOR ELEVATABLE DRAWWORKS, MASTS AND SETBACK TOWER
(54) French Title: CHASSIS DE REMORQUE SUR ROUES POUR TREUILS DE FORAGE, MATS ET TOURS TELESCOPIQUES
Status: Expired
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 20/112
(51) International Patent Classification (IPC):
  • E04H 12/34 (2006.01)
  • E04H 12/10 (2006.01)
(72) Inventors :
  • PATTERSON, BRADLEY C. (United States of America)
(73) Owners :
  • PATTERSON, BRADLEY C. (Not Available)
(71) Applicants :
(74) Agent: GEORGE H. RICHES AND ASSOCIATES
(74) Associate agent:
(45) Issued: 1980-09-16
(22) Filed Date: 1979-02-07
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract


WHEELED PORTABLE TRAILER SUBSTRUCTURE
FOR ELEVATABLE DRAWWORKS, MASTS AND SETBACK TOWER
Abstract of the Disclosure
A first and second mobile trailer means are secured
together for forming a base substructure support for a mast, set-
back tower and drawworks. A working floor is provided in elevated
position above the base substructure support when the mast, set-
back tower and drawworks is in position to conduct well operations
the telescoping mast and setback structure is pivotally carried
on the first trailer means and a drawworks is pivotally carried
by the second trailer means. A power and rig up arrangement
is provided to elevate in a desired sequence the mast, setback
structure and drawworks to a desired position for securing on
the base substructure support formed by the first and second
trailer means for conducting well operations.


Claims

Note: Claims are shown in the official language in which they were submitted.


What is claimed is:
1. In a portable well drilling and workover apparatus
including a mast, drawworks and setback structure which may
be raised to provide an elevated working floor for conducting
well operations the invention comprising:
a. first trailer means;
b. second trailer means;
c. means for positioning said first and second trailer
means together to form a base substructure support for the
apparatus;
d. means pivotally connecting the mast and setback
structure on said first trailer means whereby they may be trans-
ported in reclined position and then elevated when desired;
e. support means pivotally suporting said drawworks
on said second trailer means;
f. sheave means on said mast for receiving a line
thereover secured at one end to said setback structure resting
on said first trailer means and connected with power means at
its other end to first elevate said setback structure; and
g. means to secure said setback structure in elevated
position on said first trailer means.

2. The invention of claim 1 including:
a. sheave means on said setback structure and said
drawworks platform whereby a line may be secured to said setback
structure and extended around said sheave on said drawworks
platform and around said sheave means on said setback structure
and connected to a power source for elevating said drawworks
and said support therefor; and




b. means to secure said drawworks support means in
elevated position on said second trailer means.
3. The invention of claim 2 including:
a. A traveling block in said mast and having a line
extending therefrom, over the crown block and connected to said
drawworks;
b. a sling connected at one end to the resting mast
on said first trailer means, extended over a sheave on said
elevated setback structure and connected at its other end to
said traveling block whereby said elevated drawworks may be
employed to elevate said mast up over said setback structure; and
c. means to secure said mast in elevated position
on said first trailer means.

4. The invention of claim 3 including laterally
extending brace means pivotally carried by at least one of
said trailer means for providing additional stability to the
base substructure.

16

Description

Note: Descriptions are shown in the official language in which they were submitted.


Summary of the Invention
A trailer supported, telescoping, elevatable mast
and drawworks arrange~ent has been provided and employed in
the prior art; however, generally speaking such structures have
necessitated the addition of a base support substructure before
the mast and drawworks are properly positioned to conduct well
drilling operations. The base support structure heretofore
has been formed by adding a plurality o~ structural members
at the drilling site to provide proper support for the trailers
or bet~een the trailers and the elevated mast and drawworks
to structurally support the drawworks and mast load during we.ll
2~ operations. Also, a drawworks, setbac~ structu~-~ a~ aS~ ve
been employed to provide a working floor at a desired elevation
above a base substructure constructed at the drilling site so
that blowout preventors and other equipment may be positioned
between the elevated working floor and the substructure and
to enable other desirable operations in such arrangement to
be conducted.


-1- ~.,

1~85575

Also, in prior art arrangements, an A frame has been
employed to assist in elevating the mast to final position.
The present invention provides a mobile trailer sup-
ported telescoping mast and setback structure as well as a
trailer supported drawworks wherein the mobile trailers are con-
structed and arranged to form the base substructure support
for the mast, setback tower and drawworks when in elevated
position. This eliminates the necessity oE building a separate
substructure at the location and substantially shortens the
rig up and rig down time re~uired to enable the arrangement
to be placed in operation for conducting well operations and
to enable the arrangement to be removed from the well location
after such operations have been conducted. The drawworks and
mast are elevated in a desired sequence with the setback tower,
thus eliminating the necessity o~ an A frame.
An o~ject of the present invention is to provide a
substructure to support an elevated drawworks, sstback tower
and mast structure which is formed by pinning or connecting
together two portable wheeled trailers which rest directly on
the ground and form the base substructure support for the draw-
works, setback tower and mast.
An object o~ the present invention is to provide a
substructure to support an elevated drawworks, setback tower
and mast structure which is formed by pinning or connecting
2~ together two portable wheeled trailers which rest directly on
t`ne ground and form the base su~structure support E~r th~ draw-
workc, setback tower and mast and wherein one trailer is pro-
vided with the telescoping mast and the setback tower and the
other trailer is provided with the elevatable drawworks.


1~8~575

An object of the present invention is to ~rovide a
substructure to support an elevated dra~orks, se~back tower
and mast structure which is formed by pinning or connecting
together two portable wheeled trailers which rest directly on
the ground and form the base su~structure support for the draw-
works, setback tower and mast and wherein one trailer is pro-
vided with the telescoping mast and the setback towcr and the
other trailer is provided with the elevatable drawworks and
wherein the trailer supporting the telescoping mast assists
in maintaining it in reclining position on the trailer until
the mast is elevated.
An object of the present invention is to provide a
substructure t'o support an elevated drawworks, setback tower.
and ~ast structure which is formed by pinning or connecting
lS together two portable wheeled trailers which rest directly on
the ground and foxm the base substructure support for the draw-
works, setback tower and mast, and an arrangement whereby the
mast may be elevated without the use of an A fra~e.
An object of the present invention is to provide a
substructure to support an elevated draw~oxks, sethack tower
and mast structure which is formed by pinning or connecting to-
gether two portable wheeled trailers which rest directly on the
gro~nd and form the base substructure support for the drawworks,





1~ 5575

setback tower and mast, and an arran~ement whereby the mast
is elevated with the drawwor~s and setback tower.
An object of the present invention is to provide a
substructure to support an elevated drawworks, setback tower
and mast structure which is formed by pinning or connecting
together two portable wheeled trailers which xest directly on
the ground and form the base substructure support for the draw- -
works, setback tower and mast, and an arrangement where~y the
mast is elevated with the drawworks and setback tower and
with the drawworks in either an elevated or non-elevated posi-
tion in relation to the trailers.
Other objects and advantages of the present invention
will become more readily apparent from a consideration of the
following description and drawings.
rief_Description of the Drawings
Fig. 1 is a view showing one of the portable wheeled
trailer means with a ~ ast pivotally supported thereby
and astride a setback structure pivotally mounted on the trailer;
Fig. 2 is a view similar to Fig, 1 but sh~wing a
portion of the trailer resting on the ground sur~ace to form
part of the base structure;
Fig. 3 illustrates the position of the setback struc-
ture or tower when it has been pivoted to an upright position;
Fig. 4 illustrates a second trai~er means with a draw-

works pivotally supported thereon moved into position adjacentthe first drawworks;
Fig, 5 shows the first and second trailer means secure~
together and the drawworks connected for elevatin~ it to its
final position;
3~

1~35575

Fig. 6 is a view showing one sequence of elevating
the dra~orks and mast with the drawwor~s elevated to its final
position and secured with the setback structure and the mast
connected for elevating it to its fixed position;
Fig. 7 is a view illustrating the sling and rig up
arrangement for elevating the mast with the drawworks and set
back tower and more particularly shows the relationship of
the various components for raising or elevating the ~ast after
the drawworks has been elevated;
Fig. 7A shows the mast, drawworks and set~ack tower
in elevated position on the trailers which are secured together
to form the base substructure for the mast, dra~works and set-
back tower;
Fig. 8 is an end view looking towards the base suk-
structure illustrating the lateral brace means pivotally sup-
ported on the trailers to assist in maintaining the base sub-
structure in position as well operations are conducted;
Pig. 9 is a view on the line 9-9 of Fig. 7A illus-
trating the elevated working floor area formAed by the setback
structure, mast and drawworks;
Fig. 10 is a view illustrating the arxangement for
raising the mast with the drawworks in the down position; and
Fig. 11 is a view illustrating the arrangement for
raising the drawworks after the mast has been elevated.
Description of the Preferred Embodiment
Attention is first directed to Fig. 1 of the drawings
wherein the first trailer means is represented generally hy
the numeral 15. The trailer 15 includes a suitable wheeled
carriage 16 formed by longitudinally and laterally spaced wheels
which carries longitudinally extending, latera~ly spaced members

~08~75

one of which is illustrated at 17. The longitudinally extending
members 17 are connected together and spaced apart by laterally
extending braces, not shown. A -_ mast referred to
generally at 20 is pivotally mounted at 21 at its lower end
and rests on the member 22 extending upwardly from the extension
18 of the longitudinally extending members 17.
A pipe setback and support structure referred to gen-
erally at 25 is pivotally supported at 26 on the trailer 15,
and the mast 20 is wide enough so that it is astride the setback
structure 25 as will be described in greater detail hereinafter.
Lateral brace means 30 are provided on each side of the trailer
15 and are pi~otally secured to such trailer 15 so that during
transport of the mast 20 and the setback tower 25 while resting
on the trailer 15, the lateral brace means 30 also rests on
the longitudinally extending members 17 for clearance of the
trailer 15 alon~ roadways and the like. This position and re-
lationship is illustrated in Figs. 1 and 2 of the drawings.
A vehicle represented by the letter V ~ay be employed
to transport the first trailer means 15 with tlle reclining mast
20 and setback structure 25 thereon as illustrated in Fig. 1.
-It will be noted that the portion 18 of the longitudinal membe~s
17 extends to a fifth wheel 19 on the truck so that the trailex
15 as well as the reclining mast 2~ and the reclining setback
tower 25 are freely pivotal relative to the vehicle V to enable
the trailer 15 and truck Y to be manuevered on a road along
wili~h i~ m~y mo~.
In Fig. 1 there is illustrated at 35 the center line
of a well relative to which the mast 20, setback structure 25
and drawworks 70 of the present invention are to be positioned,
and as seen in Fig. 1, the trailer 15 has been manuevered

1~85575
by the vehicle V into position in a manner well known in the
art so that when the components of the present invention are
positioned, they will be in proper rela.ionship relative to
the center line 35 of the well or location where well operations
are to be conducted.
It will be noted that the extension 18 of the longi-
tudinal members 17 are connected toge~her by the arrangement
referred to generally at 18a. The arrangement 18a includes
a pair of spaced members 18b and lgc which are pivotally con-

nected at their ends 18d, and 18e to the laterally spaced, lon-
gitudinal me~bers 17 of the first trailer lS and to the longi-
tudinal extensions 18 as shown in the drawingsr Locking pins
18f and 18g may be removed from the ~em~ers 18b and 18c whereupon
the members 17 of the trailer 15 are lowered to rest on the
ground by the cable 48a connected thereto and extending over
pulley 48b on mast 20 to the winch ~8 or vehicle V as illustrated
in Fig. 2~ ~ince the portion 18 is still connected to the fifth
wheel 19 of the vehicle V, the support ~2 retains its position
that it had in Fig. 1 of the drawings to maintain the telescoping
mast 20 in substantially the same relative position to the
trailer 15 and the vehicle V. When the members 17 are lowere~
to the ground and before the vehicle is disconnected, as shown
in ~ig. 2, it will be noted that the ~ast 20 is elevated by 22
as the members 17 are lowered to ground level.
After the members 17 have been lowered to the ground
as shown in ~ig. 2 and be~ore the set~ack tower 25 is elev~te~
the lateral bxace member 30 is pivoted outwardly and downwardly
to rest on the ground as shown in ~igs.3, 5 and 8 of the draw-
ings. Any suitable number of lateral braces may be employed
longitudinally of the trailer 15, and as illustrated one ~race

-- ` 1(~855 ~ ~
member 30 is provided on each side adjacent an end of the
trailer 15.
The mast 20 generally incorporates at least two
telescoping sections represented in dotted line at 20x wi~hin
the portion shown in solid line in Figs. 1 and 2 of the draw-
ings. These portions 20x are extended from the solid line portion
by a winch line or by the other means as well known in the art.
The setback tower 25 may then be moved to elevated
position by connecting separate lines 40 over sheaves 41 spaced
laterally on the mast 20 and securing one end of each line as
at 47 to each side of the setback structure 25 resting on
trailer 15 as shown in Fig. 2. The other end of the lines 40
may be connected to a winch 44 on any suitable vehicle such as
represented at V' in Fig. 4 whereupon the setback structure
25 may be elevated by pulling on the lines or cables ~0 to piv-
otally raise the setback tower 25 so that it assumes ~he position
illustrated in Fig. 3 of the drawings. It will be noted that
the setback structure 25 includes four legs two of which are
illustrated at 50 and 51 on one side of trailer 15 with two
other similar legs being provided on the other side of the
trailer 15 so that the setback structure 25 genexally for~
a rectangular box like structure when elevated as seen in Fig~
3. A lateral brace 53 is secured diagonally between the legs
S0 and 51 on each side o~ the setback t~wer 25 as sho~,n in Fig.
3 and the legs 51 are secured in the footings 51a for~ed on
the tr~iler 15 to secure the setback towex 25 in the eleva~ed
position shown in Fig. 3 of the drawings.
When it is desired to disconnect trailer 15 from vehicle
V and move the vehicle ~ from beneath the mast 20, loc~ing pins
18f and 18g are reinserted în openings 18b and 18c to thereby




--8--

1~8~5 ~ 5

retain the extension 18 in the position shown in Figs. 3 and 5.
If the extension 18 is lowered to ground level by removing the
locking pins, a support of any suitable construction as repre-
sented by the letter S in Fig. 6 may be positioned under the
mast 20 to retain it in position until it is elevated.
The second trailer 60 is moved into position by a
vehicle V' connected therewith and a~ain the second trailer
60 includes a wheeled carriage 16 for transport or ~ovement
of the trailer and drawworks pivotally supported thereon. The
second trailer 60 includes longitudinally extending, laterally
spaced beams 17a which are connected together by suitable lateral
members (not shown) to form a base substructure support for the
drawworks represented generally by the numeral 70 in Fig. 4.
The first trailer 15 and the second trailer 60 each
include suitable bracket and brace means 31 and 32 having open-
ings therein as shown so that when the first and second trailers
are positioned as illustrated in Figs. ~ thru 7A of the drawings,
the braces interfit so they may be pinned ox secured together to
form an in~egral base substructure support. After the second
trailer means 60 has been positioned adjacent the end of the
first trailer means 15, the vehicle V' supporting the secona
trailer 60 may be driven out from beneath the second trailer
60 and the members 17a of the second trailer lowered to the
ground by a winch and cable (not shown).
Thus, the first trailer 15 and second trailer 60 are
not ~r~ly s~cured togeth~r but their bodies rorm thP base sub-
structure to support the mast, setback tower and dra~orks in
elevated position as well operations are conducted as will be
described in greater detail hereinafter. It is to be noted
that substantially no additional substructure or su~ports are

5~5


provided between the elevated floor referred to generally at
80 in Fig. 9 and the base support structure formed ~y the lon-
gitudinally extending members 17, 18, and 17a of the trailer
means 15 and 60. After the first trailer means 15 and second
trailer means 60 have ~een secured together at their abutting
ends as shown in Fig. 5 by any suitable means securing the
brac~ets and braces 31 and 32, the drawworks referred to gen-
erally at 70 and the mast referred to generally at 20 may be
elevated into working position.
The drawworks 70 is carried on a support 70a pivotally
mounted on the trailer 60. The elevatable drawworks support
70a includes four legs. Legs 71a and 72 are pivotally connected
on one side of trailer 60 and similar legs are pivotally con-
nected on the other side of trailer 60. In the sequence illus-
trated in Fig. 5, lines 55 are connected to each side of the
elevated setback tower 25 adjacent the legs 51 nearest the re-
clining drawworks 70. The cables S5 are each extended over
a sheave 71 adjacent each side of the reclining drawworks support
70a and then reeved over a sheave 56 mounted adjacent the upper
end of the elevated setback tower 25 and extended beneath the
sheaves 57 in each side of the reclining mast 20 and are then
connected to a winch 4~ on the vehicle V of Fig. 1, or any other
suitable winch on a vehicle. By pulling on the cables 55 by
means of the winch 48 on the vehicle, the dra~works support
70a and drawwor~s 70 is then elevated to the position shown
in ~`ig. 6 on the trailer 60.
After the drawworks support 70a has been ele~atea
to the position as shown in Fig. 6, it is secured to the trailer
60 by the legs 72 being pinned to the footing 73. A-so a lateral
brace 74 is then positioned in an inclined relationship between

` lC85575
the legs 71a and 72 on each side of the support 70a and between
the upper end of the support 70a and the base substructure formed
by the members 17 on the second trailer 60.
Also, the ~rawworks support structure 70a may be
secured to the setback structure 25 by the brackets 25a at the
upper end of the setback tower 25 and the brackets 70b at the
upper end of the elevated drawworks support 70a which brackets
may ~e secured together by any type of linkage or pin member.
m us, the drawworks support 70a and setback tower 25 form a
1~ unitary structure when elevated and secured together as well
as having their lowex ends rigidly secured on their respective
trailers 15 and 60.
When this sequence of elevation is employed, the mast
20 may next be elevated by connecting line 59 at any suitable
point such as the points 66 on each the reclining mast 20 and
then extending such lines over the sheaves 56 on each side of
the elevated setback tower 25. The lines 59 then extend under
the sheaves 57 on each side of mast 20 and the lines 59 are then
connected to the hook 69 on the traveling block 76 in the mast
20 as illustrated in Fig. 7 of the drawings. The line 59 in
effect forms a sling. A line 77 is then extended from the
drawworks drum illustrated at 75 and over the crown block 82
on the mast 20 to be connected in a manner well known to the
traveling block 76. Thus when the cable 77 is reeved in on
the drum 75 of the drawworks, the traveling block moves in the
~3~ 2~ and ca~le 59 is pulled so that the mast 20 is ~ove~
to elevated position as illustrated in Fig. 7A of the drawings.
If desired, the line 59 may be reeved around sheave 56a on the
dra~orks support structure 70a to elevate the mas~ 20.


10855 ~ 5
As previously noted, the four legs of the ~ast 20 are
laterally spaced far apart enough so as to straddle the setback
tower 25 when the mast and the setback tower are in lowered posi-
tion on the first trailer 15 and thus when the mast 20 is moved
to its elevated position as shown in the drawings, the elevated
setback tower 25 will not interfere with such movement. After
the mast 20 has been moved to an upright position it also may
be secured to the base substructure formed by the first and
second trailer means 15 and 60 respectively b~ securin~ the
lower end of the mast legs to the beams 17 and 17a in any suit-
able manner as desired.
If desired, the sequence of elevation illustrated in
Figs. 10 and 11 ~ay be employed. If so, the set~ack tower 25 is
first elevated as shown and as previously described. The mast
20 is next elevated by connecting the sling line 59 from points 66
on the mast 20 and extending ~ around sheaves 56 on the raised
setback tower 25, under sheave 57 on mast 20 and connectin~ each
line 59 with the hook 69 on the travelling bloc~. The line 77
wound on drum 75 of drawworks 70 is reeved over sheave 56b and
extends over the crown block as shown in Fig~ 7 for connection
with the traveling block 76. When the cable 77 is reeved in on
drum 75, mast 2~ i5 raised to the position of Fig. 11 for con-
nection with the trailer 15 as previously described.
The drawworks 7~ and its support structure 70a is
elevated on trailer 60 by connecting lines 55 as at 55c to each
sid~ OL s~bac~ ~ower ~5. The lines 55 are then ree~ r~
sheaves 71b on drawworks support structure 70a and then over
sheaves 55d on each side of the setback tower 25, ana then under
sheave 55f on the lower end of the setback tower 25 to be con-
nected to winches (not shown) as illustrated at 55g. ~hen the
lines 55 are reeved in on the winches, the drawworks 70 and its




-12-

5575
support structure 70 are elevated to the position i~lustrated
in Fig. 6. It is then connected to the setback tower and trailer
60 as previously described to secure it in position.
The drawworks support 70a, the mast 20 and the setback
tower 25 can each be provided with suitable grill or floor
plate material as illustrated generally at 100 in Fig. 9 to
form a work area referred to generally at 80 which is elevated
relative to the base substructure for~ed by the structure
of the first and second trailer means 15 and 60. It is to be
also noted that the mast 20 includes suitable rotary table
support members 86 and 87 as illustrated in Fig. 9 of the draw-
ings. If desired the setback structure 25 may have a slotted
portion illustrated at 88 formed in its floor 100 to enable
tubular members to be positioned vertically therein as they
are removed from the well, or to enable tubular members to be
positioned vertically in the setback tower 25 and connected
into the well string as may be desired.
It is to be also noted that the floor structure 100
carried by the setback tower 25 includes laterally extending
portions 101 as more clearly illustrated in Fig. 8 of the
drawings. The laterally extending portions 101 are pivotally
secured at 10~ adjacent the outer edges o~ the setback tower
25 as shown so that such floor portions 101 can be ~oved into
operating position after the setbac~ tower 25 has been raised
to an elevated position. Of course when the setback tower 25
i~ r~iinis~g Oll tne tr~iler ~5, the floor por~ions ~0~ are
pi~oted over and onto the reclining setbac~ tower 25 in a manner
so as to not interfere with movement of the trailer 15 along
a road or highway.
~0

( 1~85575

The foregoing arrangement provides a mobile trailer
support structure for a portable telescoping mast, drawworks,
and setback tower which can be moved from location to location
with ease.
S The trailers can be positioned on a well location, and
secured together. Their frames are lowered to the ground to
form the base substructure for the mast, setback tower and
drawworks when they are elevated to working position for con-
ducting well operations.
The foregoing disclosure and description of the
invention are illustrative and explanatory thereof, and various
changes in the size, shape, and materials as well as in the
details of the illustrated construction may be made without
departing from the spirit of the invention.




-14-

Representative Drawing

Sorry, the representative drawing for patent document number 1085575 was not found.

Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 1980-09-16
(22) Filed 1979-02-07
(45) Issued 1980-09-16
Expired 1997-09-16

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $0.00 1979-02-07
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
PATTERSON, BRADLEY C.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

To view selected files, please enter reCAPTCHA code :



To view images, click a link in the Document Description column. To download the documents, select one or more checkboxes in the first column and then click the "Download Selected in PDF format (Zip Archive)" or the "Download Selected as Single PDF" button.

List of published and non-published patent-specific documents on the CPD .

If you have any difficulty accessing content, you can call the Client Service Centre at 1-866-997-1936 or send them an e-mail at CIPO Client Service Centre.


Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1994-04-12 6 143
Claims 1994-04-12 2 59
Abstract 1994-04-12 1 25
Cover Page 1994-04-12 1 10
Description 1994-04-12 14 592