Notable punk rock bands, such as Crass, Conflict, Sex Pistols, The Clash, Dead Kennedys, Black Flag, Refused, American Standards, Discharge, MDC, Aus-Rotten, Anti-Flag, and Leftöver Crack have used political and sometimes controversial lyrics that attack the establishment, sexism, capitalism, racism, speciesism, colonialism, and other phenomena they see as sources of social problems.