UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
"Washington, DC 20549"
SCHEDULE 13G
Under the Securities and Exchange Act of 1934
(Amendment No. ______________)*
Plains Resources Inc.
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(Name of Issuer)
Common
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(Title of Class of Securities)
726540503
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(CUSIP Number)
December 31, 2002
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(Date of Event Which Requires Filing of this Statement)
Check the apprpriate box to designate the rule pursuant to
which this Schedule is filed:
[X] Rule 13d-1 (b)
[ ] Rule 13d-1 (c)
[ ] Rule 13d-1 (d)
* The remainder of this cover page shall be filled out for a
reporting person's initial filing on this form with respect to
the subject class of securites, and for any subsequent amendment
containing information which would alter the disclosures provided
in a prior cover page.
The information required in the remainder of this cover page
shall not be deemed to be "filed" for the purpose of Section 18
of the Securities Exchange Act of 1934 ("Act") or otherwise
subject to the liabilities of that section of the Act, but shall
be subject to all other provisions of the Act (however, see
the Notes.)
1 Name of Reporting Person / IRS Identification Number:
Advisory Research, Inc. / 36-2831881
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2 Check the Appropriate Box if a Member of a Group (a) [ ]
(See Instructions) (b) [X]
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3 SEC Use Only
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4 Citizenship or Place of Organization
Delaware
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Number of
5 Sole Voting Power
Shares 1,181,894 Shares
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Beneficially
6 Shared Voting Power
Owned By 0 Shares
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Each
7 Sole Dispositive Power
Reporting 1,181,894 Shares
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Person
8 Shared Dispositive Power
With 0 Shares
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9 Aggregate Amount Beneficially Owned by Each Reporting Person
1,181,894 Shares
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10 Check if the Aggregate Amount in Row (9) Excludes Certain
Shares [ ] (See Instructions)
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11 Percent of Class Represented by Amount in Row (9)
4.91%
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12 Type of Reporting Person
IA
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Item 1 (a) Name of Issuer: Plains Resources Inc.
Item 1 (b) Name of Issuer's Principal Executive Offices:
500 Dallas Street
Suite 700
Houston, TX 77002
Item 2 (a) Person Filing - Advisory Research, Inc.
Item 2 (b) Address - 180 North Stetson St., Suite 5780
Chicago, IL 60601
Item 2 (c) Citizenship - Advisory Research, Inc. is a
Delaware Corporation
Item 2 (d) Title of Class of Securities - Common
Item 2 (e) CUSIP Number - 726540503
Item 3 If this statement is filed pursuant to Rules
13d-1(b) or 13d-2(b), check whether the person
filing is a:
(a) [ ] Broker or Dealer registered under Section
15 of the Act
(b) [ ] Bank as defined in Section 3(a)(6) of the
Act
(c) [ ] Insurance Company as defined in Section
3(a)(19) of the Act
(d) [ ] Investment Company registered under
Section 8 of the Investment Company Act
(e) [X] Investment Advisor in accordance with
section 240.13d-1(b)(1)(ii)(E)
(f) [ ] Employee Benefit Plan or Endowment Fund
in accordance with section 240.13d-1(b)
(1)(ii)(F)
(g) [ ] Parent Holding Company or Control Person
in accordance with secton 13d-1(b)
(1)(ii)(G)
(h) [ ] A savings association as defined in
section 3(b) of the Federal Deposit
Insurance Act
(i) [ ] A church plan that is excluded from
the definition of an investment company
under section 3(c)(14) of the Investment
Company Act of 1940
Item 4 Ownership
(a) Amount Beneficially Owned:
Advisory Research, Inc. 1,181,894 Shares
(b) Percent of Class 4.91%
(c) Number of shares as to which reporting person has:
(i) Sole Voting Power 1,181,894 Shares
(ii) Shared Voting Power 0 Shares
(iii) Sole Dispositive Power 1,181,894 Shares
(iv) Shared Dispositive Power 0 Shares
Item 5 Ownership of Five Percent or Less of a Class:
If this statement is being filed to report the fact
that as of the date hereof the reporting person has
ceased to be the beneficial owner of more than five
percent of the class of securities, check the
following [X]
Item 6 Ownership of More than Five Percent on Behalf of
Another Person: Not Applicable
Item 7 Identification and Classification of the Subsidiary
Which Acquired the Security being Reported on by the
Parent Holding Company: Not Applicable
Item 8 Identification and Classification if Members of
the Group: Not Applicable
Item 9 Notice of Dissolution of Group: Not Applicable
Item 10 Certification
By signing below I certify that, to the best of my
knowledge and belief, the securities referred to
above were acquired and are held in the ordinary
course of business and were not acquired and are
not held for the purpose of or with the effect of
changing or influencing the control of the issuer
of such securities and were not acquired and are
not held in connection with or as a participant
in any transaction having such purposes or effect.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this
statement is true, complete and correct.
February 12, 2003
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Date
/s/ Brien M. O'Brien
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Signature
Brien M. O'Brien, Chairman
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Name/Title