 Complete the following phrase:  The first official World Junior Championships for players under 20 years of age was held in 1977. Unofficial tournaments, which were not IIHF-sanctioned and teams were eligible to participate by invitation only, had been contested between 1974 and 1976. It began as a relatively obscure tournament, but soon grew in popularity, particularly in Canada. The most infamous WJC event was the Punch-up in Piestany in 