Does anyone know where I can find a good references on the various AI implementations of the ghosts in Pacman? Or if not have any suggestions on ways they might approach doing such AI? Here is a little of wait I'm aiming to achieve.

Ghost1 = Chaser -> main goal is to eliminate the player.
Ghost2 = Guardian -> main goal is to guard the pellets.
Ghost3 = Sentry -> main goal is to guard the area previously occupied by pelletes.
Ghost4 = Wanderer -> has no real goal, just wanders the map and chases the player if he gets too close.