 Complete the following phrase:  In 1993, Garry Kasparov and Nigel Short broke ties with FIDE to organize their own match for the title and formed a competing Professional Chess Association PCA. From then until 2006, there were two simultaneous World Championships and respective World Champions: the PCA or classical champions extending the Steinitzian tradition in which the current champion plays a challenger in a series of games, and the other following FIDEs new format of many players competing in a large knockout tournament to determine the champion. Kasparov lost his PCA title in 