Exhibit 4(a) STATE OF DELAWARE CERTIFICATE OF LIMITED PARTNERSHIP o The Undersigned, desiring to form a limited partnership pursuant to the Delaware Revised Uniform Limited Partnership Act, 6 Delaware Code, Chapter 17, do hereby certify as follows: o First: The name of the limited partnership is Atlas America Public #12-2003 Limited Partnership o Second: The address of its registered office in the State of Delaware is 110 S. POPLAR STREET, SUITE 101 in the city of WILMINGTON, DE 19801 The name of the Registered Agent at such address is ANDREW M. LUBIN o Third: The name and mailing address of each general partner is as follows: ATLAS RESOURCES, INC. MANAGING GENERAL PARTNER 311 ROUSER ROAD, P. O. BOX 611 MOON TOWNSHIP, PA 15108 o In Witness Whereof, the undersigned has executed this Certificate of Limited Partnership of Atlas America Public #12-2003 Limited Partnership as of July 10, 2003. Partnership Name By: ATLAS RESOURCES, INC. MANAGING GENERAL PARTNER /s/ Frank P. Carolas ----------------------------------------- Frank P. Carolas, Executive Vice President State of Delaware Secretary of State Division of Corporations Delivered 12:30 PM 07/15/2003 FILED 12:30 PM 07/15/2003 SRV 030464391 - 3681735 FILE