I'm sorry to see that Mary Travers of the 60s group Peter, Paul, and Mary has passed away. There's plenty of detailed information on the 'net for anyone interested in her, or the group's, history. I just thought I'd mention that even for a pretty hard-core hard rock lover like me, Puff the Magic Dragon and Leaving on a Jet Plane stand out in memory of the 60s and early 70s, and Mary's part of the three-part harmony stands out particularly.
An awful lot of my Vietnam War-era peers have memories, poignant or otherwise, with Leaving on a Jet Plane as the background music.
"I don't know when I'll be back again
Oh, babe, I hate to go."