the first paper is history of a theoretical model of coupled oscillators called the Kuramoto model, which demonstrates threshold phase-locking of individual oscillators to the average population phase.
the first 6 or so sections are a good introduction so I would recommend reading them. Later sections give further analysis but it gets more complicated and i don't think it's as important for our interests. we probably won't focus much on this for the meeting.
the second paper analyzes a theoretical circuit for synchronizing populations of repressilators, demonstrating a phase transition similar to that seen in the Kuramoto model