Sheffield, April 29: World number five Mark Williams reached the semifinals of the World Snooker Championship for the second year running with a 13-9 victory over 1997 champion Ken Doherty last night.Doherty made a determined comeback after trailing 7-1 at the end of the first session, reducing Williams' lead to four frames at 11-7.But the 29-year-old Irishman was unable to completely bridge the gap and Williams finished the match with a flourish, stroking in a break of 97.It was sweet revenge for the Welsh left-hander who was beaten by Doherty at the semifinal stage last year.``I've got a bit more experience and I've won a few more tournaments since then,'' Williams said.Ronnie O'Sullivan set his sights on his first world title after beating former champion John Parrott in the quarter-finals.Resuming with an 11-5 overnight lead, O'Sullivan saw his advantage cut to three frames at 12-9.But Parrott's comeback hopes were killed off when O'Sullivan won the 22nd frame to complete a 13-9 victory.O'Sullivan said: ``The season hasn't been as successful as it could have been. But that's only down to myself and I'd like to put matters right by lifting the world title.''O'Sullivan is bidding to become the first English player to win the title since Parrott's success eight years ago.
