Name the 2008 for wta premier mandatory tournaments of 2007
CREATE TABLE "singles_performance_timeline" (
  "tournament" text,
  "2007" text,
  "2008" text,
  "2009" text,
  "2010" text,
  "2011" text
);
SELECT "2008" FROM "singles_performance_timeline" WHERE "2007"='wta premier mandatory tournaments';