What is the low rebound total for players from Oklahoma before 1975?
CREATE TABLE "a" (
  "player" text,
  "pos" text,
  "from" real,
  "school_country" text,
  "rebs" real,
  "asts" real
);
SELECT MIN("rebs") FROM "a" WHERE "school_country"='oklahoma' AND "from"<1975;