When Rufus and Lucy go to the Black Liberation Army office, Rufus tells her to wait outside and avoid eye contact with anyone. This is the same thing she said to him in "Pilot (2016)".
This is the first time Rufus speaks his full name, Rufus Carlin, and he does so in a phone booth. This is very probably a reference to George Carlin, who plays the character Rufus in the time travel movie Bill & Ted's Excellent Adventure (1989). In that movie, the time machine is a phone booth.
When Rufus enters the D.C. branch of the Black Liberation Army, he uses the alias "Kanye" after rapper/producer Ye, known as Kanye West at the time.
The Twin Towers in Rosslyn, Virginia are visible in the view from Capitol Hill. They weren't completed until 1980.
Benjamin Cahill tells Rufus that the missing 18 1/2 minutes from the tapes was the secretary's fault. While Nixon's secretary did take the blame for it, the way that she said it happened, while possible, is very unlikely.