user: Question: What years did Birger Ruud win the FIS Nordic World Ski Championships?
Columns: ['Winner', 'Country', 'Winter Olympics', 'FIS Nordic World Ski Championships', 'Holmenkollen']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Birger Ruud', 'Norway', '1932, 1936', '1931, 1932, 1935, 1936, 1937, 1948', '1932']
SQL:

assistant: SELECT "FIS Nordic World Ski Championships" FROM "Table" WHERE "Winner" = 'Birger Ruud';