Any doented proof Vietnam Vets was spit upon by either Left wing or Right wing?

I'm a Vitenam veteran. I served in the US Army from 1966-1974. I can say that I was never spat on by anyone nor was I ever called names. In the entire eight years I was in the army I never even knew a fellow soldier to whom such a thing happened. This is just my personal experience and I could not possibly know all of the soldiers. I think if it happened it was very rare. Oh yes, I was there in Vietnam during the 68 Tet offensive.