MIL-H-45374D (AMENDMENT-2), MILITARY SPECIFICATION: HOWITZER, MEDIUM, SELF-PROPELLED, 155-MM: M109, M109A1, M109A1B, M109A2, M109A3, AND M109A5 (29-MAR-1991)
MIL-H-45374D (AMENDMENT-2), MILITARY SPECIFICATION: HOWITZER, MEDIUM, SELF-PROPELLED, 155-MM: M109, M109A1, M109A1B, M109A2, M109A3, AND M109A5 (29-MAR-1991).