It was my intention to summarize the history of Special Forces in Vietnam. I found this publication that was written shortly after Special Forces departed Vietnam in 1971 to clearly depict the history of SF during the Vietnam War era. It can be accessed at:
http://www.history.army.mil/books/Vietnam/90-23/90-23C.htm

Vietnam Studies
U.S. Army Special Forces
1961-1971

CMH Publication 90-23
Department of the Army
Washington, D.C. 1989 (First Printed, 1973)