technical manual Operator's Manual (Crew) for Howitzer, Medium, Towed: 155MM, M198 (1025-01-026-6648) technical manual Operator's Manual For Howitzer, Medium, Self-Propelled: 155-MM, M109 (2350-00-440-8811) ; 155-MM, M109A1 (2350-00-485-9662) ; 155-MM, M109A3 (2350-01-031-8851)