Chased by a lion and other pursuit-evasion problems I am looking for a reference (book or article) that poses a problem that seems to be a classic, in that I've heard it posed many times, but that I've never seen written anywhere: that of the possibility of a man in a circular pen with a lion, each with some maximum speed, avoiding capture by that lion. References to pursuit problems in general would also be appreciated, and the original source of this problem.

Since you're asking for a reference, perhaps this will do?

Wolfram Mathworld says the problem was listed by Rado in 1925. The reference is on the problem description page, here.