The specific "paper" mentioned in your query refers to the joint academic paper these two characters are fighting over throughout the episode. Ultimately, their bickering over MPC vs. PID exemplifies their incompatible working relationship.
Bob Newhart’s cameo as Professor Proton’s ghost directly connects to TBBT (Season 6, Episode 22). This episode reinforces that Sheldon’s lifelong mentor was a figment of his imagination but a source of real wisdom. young sheldon s04e17 mpc