What is the 1991 when 1992 and 1990 are 1R?
CREATE TABLE "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,
  "career_sr" text
);
SELECT "1991" FROM "singles_performance_timeline" WHERE "1992"='1r' AND "1990"='1r';