Thanks much to all of you who replied. With the help of a few of Mark's fellow volunteers,Paul S. and others I spent a good six months in 2011 sifting through PC documents ,letters- diaries and photos. In the end I was able to make a pretty compelling case about how, when and where he "disappeared". Looking back now, some 50 yrs. after the conflict in Vietnam, it seems curious that no one in an administrative position ventured to ask the obvious question , " Why "... at least not officially. All of the 1000 Kodak slides are still sitting in the box where he left them. I'll contact those of you who I can. My e-mail is clraymaker@gmail.com