This episode takes place in December 1967 and January 1968.
When Betty is waiting in the crash pad for Sandy, a character "Zal" returns. He proceeds to tell Betty that Sandy sold him the violin. He says Betty can't "grok" their lifestyle. "Grok" is a word coined by Robert A Heinlein in his novel "Stranger in a Strange Land." The book was absorbed by the counter-culture and grok was used everywhere. Grok basically means to totally and absolutely understand a situation.
After the memorial, Roger asks his daughter Margaret "Where's Skeezix?" when he sees that Brooks and Ellery are gone. Roger is likely referring to Ellery. Skeezix is a character from the old comic strip "Gasoline Alley (1951)" who was abandoned on a doorstep as a baby.