What is the 1989 result of the tournament in which Katerina Maleeva finished 4r in 1991?
CREATE TABLE "grand_slam_singles_performance_timeline" (
  "tournament" text,
  "1984" text,
  "1985" text,
  "1986" text,
  "1987" text,
  "1988" text,
  "1989" text,
  "1990" text,
  "1991" text,
  "1992" text,
  "1993" text,
  "1994" text,
  "1995" text,
  "1996" text,
  "1997" text
);
SELECT "1989" FROM "grand_slam_singles_performance_timeline" WHERE "1991"='4r';