Oscar Ruiz, who will referee Korea's World Cup group D opening match against Poland Tuesday, is a veteran match official with eight years of international experience. Ruiz, 33, built up his career at the 1999 FIFA Confederations Cup in Mexico and the Copa America held in the same year in Paraguay. Most rect recently, he officiated five World Cup preliminaries in the South American and Asian regions. The former lawyer-turned Colombian referee is well known for his cool judgment on the pitch. With many appearances at international club matches in European and South American regions, he is also said to have a nice sense of control over international matches. Elise Doriri of Vanuatu and Leif Lindberg of Sweden were appointed as assistant referees of the match. Doriri, a full-time salesman, made his debut at an international soccer tournament in 1999. Although he has refereed at only four Oceanic regional preliminaries for this year's World Cup, Doriri said he would do his best to make only accurate calls. Lindberg, a store owner, is a veteran who has cultivated his experience as a soccer referee in European leagues since 1996. He counts the European Championship 2000 Final as one of his fondest memories.