Yippees = Cowboy books ?
Training manuals = War books.
The standard issue at the time was "Edge" for the yippees and Sven Hassell for the War books.
This all went out into the bottom of the trench when "Chicken Hawk" was published.
Not only was the story of a HU1 pilot in the Nam amazing, the writer gave a diagramatic break down of the Helo controls but also how and why you use them.
The Helo's at the time were support ops only, but they found that flying empty to pick up pax in hot LZ's was getting them shot out of the sky so it led to arming the Helo's and eventually having the HU G gunship and cobra developed.
When I was a BN Co. my Brigade Executive Officer was Walter (Joe) Marm, the only person awarded the Medal of Honor for that battle. Interestingly enough, I served with him at the Mountain Ranger Camp in Dahloniga, GA when we were both Lieutenants in 1966.