 Complete the following phrase:  The games of the tournament follow the rules of the International Ice Hockey Federation IIHF, which differ slightly from the rules used in the NHL. In the mens tournament, Canada was the most successful team of the first three decades, winning six of seven gold medals from 1924 to 1952. Czechoslovakia, Sweden and the United States were also competitive during this period and won multiple medals. Between 1920 and 1968, the Olympic hockey tournament was also counted as the Ice Hockey World Championship for that year. The Soviet Union first participated in 