Mr. David Nakles The RETEC Group, Inc. One Monroeville Center, Suite 1015 Monroeville, PA 15146 The RETEC Group, Inc.

Exhibit 10.6.d

Xx. Xxxxx Xxxxxx

The RETEC Group, Inc.

Xxx Xxxxxxxxxxx Xxxxxx, Xxxxx 0000

Xxxxxxxxxxx, XX 00000

The RETEC Group, Inc.

000 Xxxxx Xxxxxx

Xxxxxxx, XX  00000

Attn:  President

Re:      Modification to that Certain 2005 Modified Agreement

Dear Gentlemen:

Atlanta Gas Light Company (“AGLC”)  hereby proposes, as set forth below, to make a modification to the 2005 Modified Agreement between AGLC and Retec, as the 2005 Modified Agreement is identified in that certain letter agreement between AGLC and Retec attached hereto.

 The last paragraph of Section 1 Term is hereby amended by deleting “June 30, 2005” in all three instances in which it appears therein and substituting therefore in all such three instances “July 31, 2005.”

Except as modified herein, all terms, conditions, responsibilities, and obligations of the Parties set forth in the 2005 Modified Agreement shall remain in full force and effect. 

If you are in agreement with the proposed modifications set forth above, please so signify by signing on behalf of Retec in the space provided below.  If you are in agreement, the effective date of the modifications will be June 30, 2005.

                                                                                    Sincerely,

                                                                                    Atlanta Light Company

                                                                                    By: Xxxxxxx Xxxxx

                                                                                    Title: President

Agreed and Accepted

The Retec Group, Inc.

By: Xxxxxxx X. Xxxxx

Title: President