The Embassy World Professional Snooker Championship from the Crucible Theatre, Sheffield Two of the semi-finalists are already known. Tonight two more will qualify. Will one of them be ALEX HIGGINS ? Can RAY REARDON put a disappointing season behind him? Will TONY KNOWLES and KIRK STEVENS reach the semi-finals for a second time in their careers? DAVID VINE introduces live coverage of one of tonight's quarter-final nine-frame sessions.