The book that Tony finds in the men's bathroom during his dream is The Valachi Papers, written by Peter Maas. It is the famous book based on the testimony of Joe Valachi, the first member of the Mafia to turn state's evidence and who confirmed the existence of the American Mafia. It is seen again when Tony states he's done his homework.
The person at the other end of the phone at the start of Tony's dream is David Chase.
Matthew Weiner asked David Chase to direct this episode, but Chase refused because it was too much of an important episode to be directed by a first-timer.
When Tony checks behind the toilet for a gun, it is a reference to The Godfather when Michael Corleone has a gun taped to the back of the toilet in the restaurant.
When Tony and Finn's father (i.e. Vin Makazian) go to the bathroom, Annette Bening says, "I don't want my husband coming back with just his cock in his hand." This is a reference to the Godfather (1972), when Sonny says to Clemenza, "I don't want my brother coming out of that toilet with just his dick in his hands, alright?"