Which country has a FIS Nordic World Ski Championship before 1989, was in the winter Olympics before 1980, and has a Holmenkollen of 1956?
CREATE TABLE "men_s_15_km" (
  "winner" text,
  "country" text,
  "winter_olympics" real,
  "fis_nordic_world_ski_championships" real,
  "holmenkollen" text
);
SELECT "country" FROM "men_s_15_km" WHERE "fis_nordic_world_ski_championships"<1989 AND "winter_olympics"<1980 AND "holmenkollen"='1956';