The radical lines of three circles are concurrent in a point known as the radical center (also called the power center). This theorem was originally demonstrated by Monge. It is a special case of the three conics theorem (Evelyn et al. 1974, pp. 13 and 15). The point of concurrence of the three radical lines of three circles is the point left bracketing bar k | k' | k'' m | m' | m'' n | n' | n n' right bracketing bar : left bracketing bar k | k' | k'' n | n' | n'' l | l' | l'' right bracketing bar : left bracketing bar k | k' | k'' l | l' | l'' m | m' | m'' right bracketing bar (Kimberling 1998, p. 225).