4 Queens at Ballarat

The 2009 Ballarat Begonia Open has finished in a tie for first between Igor Goldenberg and and Erik Teichmann. They finiehd on 6/7 (+5=2) and drew their round 6 encounter. Equal third on 5.5 were Christopher Wallace Wallis, Mirko Rujevic and Bobby Cheng.
Going into the final round Goldenberg and Teichmann were tied with Leonid Sandler and Eugene Schon. Teichmann defeated Sandler while Goldenberg won a rare 4 queens game against Schon.
Oddly enough the crucial mistake for Schon was in gaining a second queen (how often would you say that!), and theory recommends the less adventurous 13. ... Bxg7