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                                                                    Exhibit 3.88


                         CERTIFICATE OF INCORPORATION

                                      OF

                                  ASTN, INC.

      FIRST: The name of the corporation is ASTN,Inc. (hereinafter the
"Corporation").

      SECOND: The address of the registered office of the Corporation in the
State of Delaware is 1209 Orange Street, County of New Castle, Wilmington,
Delaware 19801. The registered agent at such address is The Corporation Trust
Company.

      THIRD: The purpose of the Corporation is to engage in any lawful act or
activity for which corporations may be organized under the General Corporation
Law of the State of Delaware as set forth in Title 8 of the Delaware Code (the
"GCL").

      FOURTH: The total number of shares of stock which the Corporation shall
have authority to issue is One Thousand (1,000) shares of Common Stock, each
having a par value of $.10.

      FIFTH: The name and mailing address of the sole incorporator
are as follows:

            Name                  Address
            ----                  -------

      Jack E. Jacobsen         First Republic Bank Center
                               3600 Tower II
                               Dallas, Texas 75201

      SIXTH: The name and mailing address of the person who is to serve as the
sole director until the first annual meeting of the stockholders or until his
successor is elected and qualified are as follows:

            Name                  Address
            ----                  -------

      Carl Westcott            1303 Marsh Lane
                               Carrollton, Texas 75006
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      SEVENTH: The following provisions are inserted for the management of the
business and the conduct of the affairs of the Corporation and for further
definition, limitation and regulation of the powers of the Corporation and of
its directors and stockholders:

1.    The business and affairs of the Corporation shall be managed by or under
      the direction of the Board of Directors.

2.    The directors shall have concurrent power with the stockholders to make,
      alter, amend, change, add to or repeal the By-Laws of the Corporation.

3.    The number of directors of the Corporation shall be as from time to time
      fixed by, or in the manner provided in, the ByLaws of the Corporation.
      Election of directors need not be by written ballot unless the ByLaws so
      provide.

4.    To the full extent permitted by the GCL as the same exists or may
      hereafter be amended, a director of the Corporation shall not be liable to
      the Corporation or its stockholders for monetary damages for breach of
      fiduciary duty as a director. No repeal, amendment or modification of this
      provision, whether direct or indirect, shall eliminate or reduce its
      effect with respect to any act or omission of a director of the
      Corporation occurring prior to such repeal, amendment or modification.

5.    In addition to the powers and authority hereinbefore or by statute
      expressly conferred upon them, the directors are hereby empowered to
      exercise all such powers and do all such acts and things as may be
      exercised or done by the Corporation, subject, nevertheless, to the
      provisions of the GCL, this Certificate of Incorporation, and any By-Laws
      adopted by the stockholders; provided, however, that no By- Laws hereafter
      adopted by the stockholders shall invalidate any prior act of the
      directors which would have been valid if such By-Laws had not been
      adopted.

      EIGHTH: Meetings of stockholders may be held within or without the State
of Delaware as the Corporation's By-Laws may provide. The books of the
Corporation may be kept (subject to any provision contained in the GCL) outside
the State of Delaware


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at such place or places as may be designated from time to time by the Board of
Directors or in the By-Laws of the Corporation.

      NINTH: Whenever a compromise or arrangement is proposed between this
corporation and its creditors or any class of them and/or between this
Corporation and its stockholders or any class of them, any court of equitable
jurisdiction within the State of Delaware may, on the application in a summary
way of this Corporation or of any creditor or stockholder thereof or on the
application of any receiver or receivers appointed for this Corporation under
the provisions of Section 291 of the GCL or on the application of trustees in
dissolution or of any receiver or receivers appointed for this Corporation under
the provisions of Section 279 of the GCL, order a meeting of the creditors or
class of creditors, and/or of the stockholders or class of stockholders of this
Corporation, as the case may be, to be summoned in such manner as the said court
directs. If a majority in number representing three-fourths in value of the
creditors or class of creditors, and/or of the stockholders or class of
stockholders of this Corporation, as the case may be, agree to any compromise or
arrangement and to any reorganization of this Corporation as a consequence of
such compromise or arrangement, the said compromise or arrangement and the said
reorganization shall, if sanctioned by the court to which the said application
has been made, be binding on all the creditors or class of creditors, and/or on
all the stockholders or class of stockholders of this Corporation, as the case
may be, and also on this Corporation.

      TENTH: The Corporation reserves the right to amend, alter, change or
repeal any provision contained in this Certificate of Incorporation in the
manner now or hereafter prescribed by statute, and all rights conferred upon
stockholders herein are granted subject to this reservation.

      ELEVENTH:(a) Power to Indemnify in Actions, Suits or Proceedings other
Than Those by or in the Rights of the Corporation. Subject to Paragraph(C)) of
this Article Eleventh, the Corporation shall indemnify any person who was or is
a party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the Corporation) by
reason of the fact that he is or was a director or officer of the Corporation,
or is or was


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serving at the request of the Corporation as a director, officer, employee or
agent of another corporation, partnership, joint venture, trust or other
enterprise, against expenses (including attorneys' fees), judgments, fines and
amounts paid in settlement actually and reasonably incurred by him in connection
with such action, suit or proceeding if he acted in good faith and in a manner
he reasonably believed to be in or not opposed to the best interests of the
Corporation, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful. The termination of any
action, suit or proceeding by judgment, order, settlement, conviction, or upon a
plea of nolo contenders or its equivalent, shall not, of itself, create a
presumption that the person did not act in good faith and in a manner which he
reasonably believed to be in or not opposed to the best interests of the
Corporation, and, with respect to any criminal action or proceeding, had
reasonable cause to believe that his conduct was unlawful.

            (b) Power to Indemnify in Actions, Suits, or Proceed ings by or in
the Right of the Corporation. Subject to Paragraph (c) of this Article Eleventh,
the Corporation shall indemnify any person who was or is a party or is
threatened to be made a party to any threatened, pending or completed action or
suit by or in the right of the Corporation to procure a judgment in its favor by
reason of the fact that he is or was a director or officer of the Corporation,
or is or was serving at the request of the Corporation as a director, officer,
employee or agent of another corporation, partnership, joint venture, trust or
other enterprise against expenses (including attorneys' fees) actually and
reasonably incurred by him in connection with the defense or settlement of such
action or suit if he acted in good faith and in a manner he reasonably believed
to be in or not opposed to the best interests of the Corporation; except that no
indemnification shall be made in respect of any claim, issue or matter as to
which such person shall have been adjudged to be liable for negligence or
misconduct in the performance of his duty to the Corporation unless and only to
the extent that the Court of Chancery or the court in which such action or suit
was brought shall determine upon application that, despite the adjudication of
liability but in view of all the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses which the Court of
Chancery or such other court shall deem proper.


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            (C) Authorization of Indemnification. Any indemnification under this
Article Eleventh (unless ordered by a court) shall be made by the Corporation
only as authorized in the specific case upon a determination that
indemnification of the director or officer is proper in the circumstances
because he has met the applicable standard of conduct set forth in Paragraph (a)
or (b) of this Article Eleventh, as the case may be. Such determination shall be
made (i) by the Board of Directors by a majority vote of a quorum consisting of
directors who were not parties to such action, suit or proceeding, or (ii) if
such a quorum is not obtainable, or, even if obtainable, a quorum of
disinterested directors so directs, by independent legal counsel in a written
opinion, or (iii) by the stockholders. To the extent, however, that a director
or officer has been successful on the merits or otherwise in defense of any
action, suit or proceeding described above, or in defense of any claim, issue or
matter therein, he shall be indemnified against expenses (includ ing attorneys'
fees) actually and reasonably incurred by him in connection therewith, without
the necessity of authorization in the specific case.

            (d) Good Faith Defined. For purposes of any deter mination under
Paragraph (c) of this Article Eleventh, a person shall be deemed to have acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the Corporation, or, with respect to any criminal action
or proceeding, to have had no reasonable cause to believe his conduct was
unlawful, if his action is based on the records or books of account of the
Corporation or another enterprise, or on information supplied to him by the
officers of the Corporation or another enterprise in the course of their duties,
or on the advice of legal counsel for the Corporation or another enterprise or
on information or records given or reports made to the Corporation or another
enterprise by an independent certified public accountant or by an appraiser or
other expert selected with reasonable care by the Corporation or another
enterprise. The term "another enterprise" as used in this Paragraph (d) shall
mean any other corporation or any partnership, joint venture, trust or other
enterprise of which such person is or was serving at the request of the
Corporation as a director, officer, employee or agent. The provisions of this
Paragraph (d) shall not be deemed to be exclusive or to limit in any way the
circumstances in which a person may be deemed to have met the


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applicable standard of conduct set forth in Paragraph (a) or (b) of this Article
Eleventh, as the case may be.

            (e) Indemnification by a Court. Notwithstanding any contrary
determination in the specific case under Paragraph (c)of this Article Eleventh,
and notwithstanding the absence of any determination thereunder, any director or
officer may apply to any court of competent jurisdiction in the State of
Delaware for indemnification to the extent otherwise permissible under
Paragraphs (a) or (b) of this Article Eleventh. The basis of such
indemnification by a court shall be a determination by such court that
indemnification of the director or officer is proper in the circumstances
because he has met the applicable standards of conduct set forth in Paragraphs
(a) or (b) of this Article Eleventh, as the case may be. Notice of any
application for indemnification pursuant to this Paragraph (e) shall be given to
the Corporation promptly upon the filing of such application.

            (f) Expenses Payable in Advance. Expenses incurred in defending a
civil or criminal action, suit or proceeding may be paid by the Corporation in
advance of the final disposition of such action, suit or proceeding upon receipt
of an undertaking by or on behalf of such director or officer to repay such
amount unless it shall ultimately be determined that he is entitled to be
indemnified by the Corporation as authorized in this Article Eleventh.

              (g) Nonexclusivity and Survival of Indemnification. The
indemnification and advancement of expenses provided by, or granted pursuant to,
this Article Eleventh shall not be deemed exclusive of any other rights to which
those seeking indemnifica tion or advancement of expenses may be entitled under
any By-Law, agreement, vote of stockholders or disinterested directors or
pursuant to the direction (howsoever embodied) of any court of competent
jurisdiction or otherwise, both as to action in his official capacity and as to
action in another capacity while holding such office, it being the policy of the
Corporation that indemnification to the persons specified in Paragraphs (a) and
(b) of this Article Eleventh shall be made to the fullest extent permitted by
law. The provisions of this Article Eleventh shall not be deemed to preclude the
indemnification of any person who is not specified in Paragraphs (a) or (b) of
this Article Eleventh, but whom the Corporation has the power or obligation to


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indemnify under the provisions of the GCL, or otherwise. The indemnification and
advancement of expenses provided by, or granted pursuant to, this Article
Eleventh shall, unless otherwise provided when authorized or ratified, continue
as to a person who has ceased to be a director or officer and shall inure to the
benefit of the heirs, executors and administrators of such person.

            (h) Indemnification of Employees and Agents of the Corporation. The
Corporation may, to the extent authorized from time to time by the Board of
Directors, grant rights to indemnification and to the advancement of expenses to
any employee or agent of the Corporation to the fullest extent of the provisions
of this Article Eleventh with respect to the indemnification and advancement of
expenses of directors or officers of the Corporation.

            (i) Insurance. The Corporation may purchase and main tain insurance
on behalf of any person who is or was a director, officer, employee or agent of
the Corporation, or is or was serving at the request of the Corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise against any liability asserted against him
and incurred by him in any such capacity, or arising out of his status as such,
whether or not the Corporation would have the power or the obligation to
indemnify him against such liability under the provisions of this Article
Eleventh.

            (j) Meaning of "Corporation" for Purposes of Article Eleventh. For
purposes of this Article Eleventh, references to the Corporation it shall
include, in addition to the resulting Corporation, any constituent corporation
(including any constitu ent of a constituent) absorbed in a consolidation or
merger which, if its separate existence had continued, would have had power and
authority to indemnify its directors, officers and employees or agents, so that
any person who is or was a director, officer, employee or agent of such
constituent corporation, or is or was serving at the request of such constituent
corporation as a director, officer, employee or agent of another corporation,
partnership, joint venture, trust or other enterprise, shall stand in the same
position under the provisions of this Article Eleventh with respect to the
resulting or surviving corporation as he would have with respect to such
constituent corporation if


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its separate existence had continued.

      I, the undersigned, being the sole incorporator hereinbefore named for the
purpose of forming a corporation pursuant to the GCL, do make this Certificate,
hereby declaring and certifying that this is my act and deed and the facts
herein stated are true, and accordingly have hereunto set my hand this 21st day
of June, 1988.

                                    Jack E. Jacobsen,
                                    Sole Incorporator


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