How and when were the top 20 Asian countries selected for the World Cup qualifiers?

The 20 14 world cup Asian regional qualifiers are divided into five stages, with 43 teams ranked, and the top five directly advanced to the third stage. In the first round, the teams ranked 28th to 43rd in the AFC drew two rounds of home and away matches, and the eight winning teams and teams ranked 6th to 27th in the AFC entered the second round. The team that entered the second stage played two rounds of home and away games, and the winning team 15 entered the third stage. In the third stage (Top 20), 20 teams were divided into 5 groups, with 4 teams and 2 teams in each group. The competition was held in the form of round robin, and the top two teams in each group advanced. In the fourth stage, the 10 team was divided into two groups, the home and away round robin, and the top two in each group directly advanced to the World Cup finals. The third place in the two groups will play two rounds of home and away play-offs, and the winner will play two rounds of home and away play-offs with the first place in Oceania to compete for World Cup tickets.