- “How old is the shepherd?” — The problem that shook school mathematics https://mystudentvoices.com/how-old-is-the-shepherd-the-problem-that-shook-school-mathematics-ad89b565fff#.9dvv4a3ag

- Robert Kaplinsky’s 3-minute video https://www.youtube.com/watch?v=kibaFBgaPx4

- P vs. NP https://en.wikipedia.org/wiki/P_versus_NP_problem