Replying to Anyone know what this Vietnam song is...?

The other day I heard a song on some hits of the 60's and 70's radio thing, and there was this really good song pertaining to Vietnam...it sounds like just one guy and a acoustic guitar, but I don't know. The reverse stays the same and he just changes the name, it goes like...

Has anyone here, seen my old friend John?
lyrics
lyrics
lyrics

Has anyone here seen my old friend Bob?
lyrics
lyrics
lyrics
....and the whole song continues like that, I've looked all over and can't find it.