UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM U-6B-2

                           Certificate of Notification

Certificate is filed by:  Public Service Company of Oklahoma.

                  This  certificate  is notice that the above named  company has
issued,  renewed or guaranteed the security or securities described herein which
issue,  renewal or guaranty was exempted from the  provisions of Section 6(a) of
the Act and was neither the subject of a declaration  or application on Form U-1
nor included within the exemption provided by Rule U-48.

1.       Type of the security or securities ("draft," "promissory note").

                  Promissory note.

2. Issue, renewal or guaranty.

                  Guaranty of promissory notes issued by third party borrower.

3. Principal amount of each security.

                  $12,000,000 Guaranty covering $12,000,000 Line Note.

4. Rate of interest per annum of each security.

                  For each promissory note, variable interest rate of 0.5% below
                  the prime rate shall apply,  as  announced by Chase  Manhattan
                  Bank  from  time to time at its New  York,  New  York  office,
                  subject  to an  interest  rate  election  by  borrower  to pay
                  interest at LIBOR plus 250 basis points.

5. Date of issue, renewal or guaranty of each security.

                  June 2, 1998.

6. If renewal of security, give date of original issue.

                  Not applicable.

7. Date of maturity of each security. (In the case of demand notes, indicate "on
demand.")

                  February 28, 1999.

8. Name of the person to whom each security was issued, renewed or guaranteed.

                  Bank of Oklahoma, N.A.

9. Collateral given with each security, if any.

                  All  accounts,  letters  of  credit,  instruments,  negotiable
                  instruments,  general  intangibles,  contract rights,  chattel
                  paper and intellectual property rights of Numanco,  L.L.C. and
                  NSS Numanco, Inc., and all proceeds of the foregoing.

10. Consideration received for each security.

                  $12,000,000.

11. Application of proceeds of each security.

                  Working capital of Numanco, L.L.C.

12.      Indicate by a check after the  applicable  statement  below whether the
         issue,  renewal  or  guaranty  of each  security  was  exempt  from the
         provisions of Section 6(a) because of

                  a. the provisions contained in the first sentence of 
                     Section 6(b)*,

                            X

                  b. the provisions contained in the fourth sentence of 
                     Section 6(b),

                  c. the  provisions  contained  in any  rule of the  Commission
                     other than Rule U-48.



(If reporting  for more than one security  insert the  identifying  symbol after
applicable statement.)

          If the  security or  securities  were exempt  from the  provisions  of
Section 6(a) by virtue of the first  sentence of Section 6(b),  give the figures
which  indicate that the security or  securities  aggregate  (together  with all
other then  outstanding  notes and drafts of a maturity  of nine months or less,
exclusive of days of grace, as to which such company is primarily or secondarily
liable)  not more than 5 per centum of the  principal  amount and par value** of
the other securities of such company then outstanding. (Demand notes, regardless
of how long they may have been  outstanding,  shall be considered as maturing in
not more than nine months for purposes of the exemption from Section 6(a) of the
Act granted by the first sentence of Section 6(b)).

          As  of  March  31,  1998,  Public  Service  Company  of  Oklahoma  had
approximately $634,719,000 of securities outstanding (other than the $12,000,000
guaranties set forth herein). The $12,000,000 guarantees are the only securities
currently issued by Public Service Company of Oklahoma  pursuant to Section 6(b)
of the Act.  Thus,  such  securities  constitute  less  than  2.0% of the  other
outstanding securities of Public Service Company of Oklahoma.

14.      If the security or securities are exempt from the provisions of Section
         6(a) because of the fourth  sentence of Section 6(b), name the security
         outstanding  on  January 1,  1935,  pursuant  to the terms of which the
         security or securities herein described have been issued.

                  Not applicable.

15.      If the security or securities are exempt from the provisions of Section
         6(a)  because  of any  rule of the  Commission  other  than  Rule  U-48
         designate the rule under which exemption is claimed.

                  Not applicable.


                                PUBLIC SERVICE COMPANY OF OKLAHOMA
                                      (Name of company)


                                By: /s/ T. D. CHURCHWELL
                                       T.D. Churchwell
                                       President





- -----------------------------------------------------------------

         * If  reporting  for  more  than  one  security  each  security  may be
identified by symbol,  which symbol should be used for each subsequent  item. If
more  convenient,  information  may be supplied by tabular  statement  using the
serial arrangement of this form.

         ** If a  security  had no  principal  amount  or par value use the fair
market value as of date of issues of such security, and indicate how determined.