of Japan won the Individual WSC and China won the team event. The 13th World Sudoku Championship took place in the Czech Republic. In the United States, The Philadelphia Inquirer Sudoku National Championship has been held three times, each time offering a $10,000 prize to the advanced division winner and a spot on the U.S. National Sudoku Team traveling to the world championships. The winners of the event were Thomas Snyder (2007), Wei-Hwa Huang (2008), and Tammy McLeod (2009). In the 2009 event, the third-place finalist in the advanced division, Eugene Varshavsky, performed quite poorly onstage after setting a very fast qualifying time on paper, which caught the attention of organizers and competitors including past champion Thomas Snyder, who requested organizers reconsider his results due to a suspicion of cheating. Following an investigation and a retest of Varshavsky, the organizers disqualified him and awarded the third-place to Chris Narrikkattu. See also 36 Cube Blendoku Constraint satisfaction problem Cracking the Cryptic Futoshiki Glossary of Sudoku Hashiwokakero Hidato KenKen List of Nikoli puzzle types Logic puzzle Nonogram Str8ts Sudoku solving algorithms References Further reading Delahaye, Jean-Paul, "The Science Behind Sudoku", Scientific American, June 2006. Provan, J. Scott, "Sudoku: Strategy Versus Structure", American Mathematical Monthly, October 2009. Published also as a University of North Carolina technical report UNC/STOR/08/04, 2008. External links 'Sudoku Variations' from Fun With Puzzles 'Father of Sudoku' puzzles next move (BBC) Abstract strategy games Latin squares Logic puzzles NP-complete problems Computer-assisted proofs Recreational mathematics