What affiliation has an owned since larger than 1991, and also has a channel (tv/rf) of 42?
CREATE TABLE "television_stations" (
  "city_of_license_market" text,
  "station" text,
  "channel_tv_rf" text,
  "owned_since" real,
  "affiliation" text
);
SELECT "affiliation" FROM "television_stations" WHERE "owned_since">1991 AND "channel_tv_rf"='42';