Complex sentence: Derek Smart is a professional rugby league footballer who played in the 1950s, and 1960s, playing at club level for Castleford, David Smart & Andrew Howard (1 July 2000) "Images of Sport-Castleford Rugby League-A Twentieth Century History".
Split into simpler sentences: Derek Smart is a former professional rugby league footballer who played in the 1950s, and 1960s. He played at club level for Castleford, David Smart & Andrew Howard (1 July 2000) "Images of Sport-Castleford Rugby League-A Twentieth Century History".