<PAGE>   1
                                                                    EXHIBIT 3.6
                     AMENDMENT OF ARTICLES OF INCORPORATION
                                        
                                       OF
                                        
                   THE SOURCE INFORMATION MANAGEMENT COMPANY


HONORABLE REBECCA MCDOWELL COOK
SECRETARY OF STATE
STATE OF MISSOURI
JEFFERSON CITY, MISSOURI 65101

     Pursuant to the provisions of The General and Business Corporation Law of
Missouri, the undersigned Corporation certifies the following:


                                   SECTION 1

     The present name of the Corporation is The Source Information Management
Company. The name under which it was originally organized was Periodico, Inc.


                                   SECTION 2

     An amendment to the Corporation's Articles of Incorporation was adopted by
the shareholders on March 30, 1999.


                                   SECTION 3

     Section (a) of Article Four of the Articles of Incorporation is amended to 
read as follows:

     (a)  The aggregate number of shares of capital stock which the corporation
shall have authority to issue is forty-two million (42,000,000), each having a
par value of One Cent ($0.01) per share. Of such authorized shares, forty
million (40,000,000) shares are hereby classified and designated as common stock
and two million (2,000,000) are hereby classified and designed as preferred
stock.


                                   SECTION 4

     All of the 12,168,299 common outstanding shares were entitled to vote on
the foregoing amendment; 6,947,521 shares voted for said amendment, 179,964
shares voted against said amendment and 19,845 abstained from voting. The
remaining 5,020,969 common shares were not represented at the meeting. Preferred
shares have no voting rights.



<PAGE>   2
                                   SECTION 5

     The Amendment changed the number of authorized shares having a par value to
from 18,528,925 to 42,000,000.


                                   SECTION 6

     The Amendment did not provide for any exchange, reclassification, or
cancellation of issued shares, or a reduction of the number of authorized shares
of any class below the value of issued shares of that class.

     IN WITNESS WHEREOF, the undersigned, President, has executed this
instrument and its Secretary has affixed its corporate seal hereto and attested
said seal on the ______ day of April, 1999.



                                   THE SOURCE INFORMATION MANAGEMENT COMPANY



(Corporate Seal)                   By ______________________________________
                                        S. Leslie Flegel,
                                        Chief Executive Officer




Attest:



_______________________________
W. Brian Rodgers
Secretary






                                      -2-
                                   
<PAGE>   3
STATE OF MISSOURI   )
                    )SS
CITY OF ST. LOUIS   )


     I, _________________________, a Notary Public, do hereby certify that on
the ____ day of April, 1999 personally appeared before me S. Leslie Flegel who,
being by me first duly sworn, declared that he is the Chief Executive Officer of
The Source Information Management Company, that he signed the foregoing document
as Chief Executive Officer of the Corporation, and that the statements therein
contained are true.



                                            ___________________________
                                            Notary Public


My commission expires:


                                       3