20-MM automatic gun M1 and 20-MM aircraft automatic gun AN-M2 : ordnance maintenance - USA Voorschrift, Technical Manual, 9-1227 Aircraft instruments - USA Technical Manual, TM 1-413 Antiaircraft artillery target practice - USA Voorschrift, Technical Manual, No. 4-234 Coast artillery Gunners' instruction, antiaircraft gun, automatic weapon, and headquarters batteries, first and second class gunners - USA Voorschrift, Technical Manual, 4-325 Coast artillery Gunner' instruction, antiaircraft artillery, expert gunners - USA Voorschrift, Technical Manual, 4-335 Coast artillery Gunner' instruction, antiaircraft searchlight batteries, first and second class gunners - USA Technical Manual, TM 4-330 Aircraft radio shop practice - USA Voorschrift, Technical Manual, 1-470 Aircraft mechanics tools - USA Voorschrift, Technical Manual, 1-425 Aircraft hardware and materials - USA Voorschrift, Technical Manual, 1-424 Aircraft sheet metal work - USA Voorschrift, Technical Manual, 1-435 Aircraft woodwork - USA Voorschrift, Technical Manual, 1-414 Aircraft electrical systems - USA Voorschrift, Technical Manual, 1-406