The leaders of four opposition parties and 13 civic and religious organizations hold a news conference Monday at the National Assembly, urging the government to release key materials on the Cheonan sinking. From left is the Peoples Participation Party`s Lee Jae-jeong; the Creative Party of Korea`s Song Yeong-oh; main opposition Democratic Party`s Chung Sye-kyun; and the progressive Democratic Labor Party`s Kang Ki-kap.