Interzonal Tournaments

Some articles on interzonal tournaments, tournament, interzonal tournament:

Interzonal Tournaments
... The top players in each Zonal tournament would meet in the Interzonal tournament, which would typically have between 20 and 24 players ... in 1958) would qualify for the Candidates Tournament, which would take place the following year ... The winner of the Candidates tournament would play a 24-game match with the World Champion the following year, and need to win outright to gain the title ...