Birger Ruud ชนะการแข่งขัน FIS Nordic World Ski Championships กี่ปี?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
What years did Birger Ruud win the FIS Nordic World Ski Championships?It is not neccessary to use all the tables.
 table_174491_2:  (fis_nordic_world_ski_championships [ VARCHAR ] winner [ VARCHAR) ]
SELECT fis_nordic_world_ski_championships FROM table_174491_2 WHERE winner = "Birger Ruud"