Gordon L. Rottman 
Vietnam Airmobile Warfare Tactics [PDF ebook] 

In this book the author an Army veteran of Vietnam explains the composition, capabilities, equipment and missions of the US Army and Marine Corps helicopter and airmobile units in the Vietnam war and exactly how they carried out their missions. It centers on the classic airmobile assault mission: how it was planned and prepared; how the troop-carrying slicks and their gunship escorts and support teams actually operated; and the opposition and hazards that they faced on the LZ. The text is illustrated with wartime photos, organization charts, and color plates showing both the machines and the tactics that where employed.