Table:
text: Nordic skiing
Men's 15 km
Men's 15 km
Winner Country Winter_Olympics FIS_Nordic_World_Ski_Championships Holmenkollen
Hallgeir Brenden Norway 1956 1956 1956
Eero Mäntyranta Finland 1964 1964 1962, 1964, 1968
Harald Grønningen Norway 1968 1968 1960, 1961
Thomas Wassberg Sweden 1980 1980 1979, 1985
Gunde Svan Sweden 1984 1989 1985

Question: How many years did the FIS Nordic World Ski Championships last when the 1968 Winter Olympics men's 15 km were held in Norway?

Question: Which country has a 15 km FIS Nordic World Ski Championships for men before 1989, participated in the Winter Olympics before 1980 and has the 1956 Holmenkollen?