I recommend this book. Covers a lot. Tonnes of photos and gets unit specific ( e.g. Company E , 75th Infantry, "Riverine Rangers," 3d Brigade , 9th Infantry Division Tan An, 1969 "Parakeet Mission" )
A very good resource for enthusiasts, collectors and reenactors. The author is also a ex army and also sells authentic kit on ebay. I bought my NVA / VC rucksack from this fellow.