What 1995 has 1r as the 1999, and a 1998 of 4r?
CREATE TABLE "singles_performance_timeline" (
  "tournament" text,
  "1990" text,
  "1991" text,
  "1992" text,
  "1993" text,
  "1994" text,
  "1995" text,
  "1996" text,
  "1997" text,
  "1998" text,
  "1999" text,
  "2000" text
);
SELECT "1995" FROM "singles_performance_timeline" WHERE "1999"='1r' AND "1998"='4r';