
                                                                    Exhibit 4k

                      CLEAN DIESEL TECHNOLOGIES, INC.

                        NOMINEE HOLDER CERTIFICATION


The  undersigned,  a bank broker or other  nominee of Rights  ("Rights") to
purchase shares of Series B Convertible  Preferred  Stock,  par value $0.05
per share ("Series B Preferred Stock"), of Clean Diesel Technologies,  Inc.
(the "Company")  pursuant to the Rights Offering described and provided for
in the  Company's  Prospectus  dated  ______ __,  1998 (the  "Prospectus"),
hereby certifies to the Company and to ChaseMellon Shareholder Services, as
Subscription  Agent for such Rights Offering,  that (1) the undersigned has
exercised,  on behalf of the  beneficial  owners thereof (which may include
the  undersigned),  the number of Rights  specified  below  pursuant to the
Basic  Subscription  Privilege (as defined in the  Prospectus) on behalf of
beneficial  owners  of  Rights  who have  subscribed  for the  purchase  of
additional   shares  of  Series  B   Preferred   Stock   pursuant   to  the
Oversubscription   Privilege  (as  defined  in  the  Prospectus),   listing
separately below each such exercised Basic  Subscription  Privilege and the
corresponding  Oversubscription  Privilege  (without  identifying  any such
beneficial  owner),  (2) each such  beneficial  owner's Basic  Subscription
Privilege  has been  exercised  in full and (3) that each  such  beneficial
owner has indicated in writing that it resides outside the United States or
in Colorado,  Connecticut,  the District of  Columbia,  Illinois,  Indiana,
Iowa, Kansas, Maine, Maryland, Massachusetts, Nevada, New Jersey, New York,
North Carolina, Rhode Island, Vermont, Virginia, and Washington.


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                                                           Number of Shares
     Number of Shares           Rights Pursuant to            Pursuant to
       Owned on the             Basic Subscription         Oversubscription
       Record Date                  Privilege                  Privilege
       -----------                  ---------                  ---------

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Provide the following information if applicable:


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Depository Trust Company ("DTC")
Participant Number


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DTC Basic Subscription Confirmation
Number(s)
