Which tournament's 2001 and 2006s were a?
CREATE TABLE "doubles_performance_timeline" (
  "tournament" text,
  "1998" text,
  "1999" text,
  "2000" text,
  "2001" text,
  "2002" text,
  "2003" text,
  "2004" text,
  "2005" text,
  "2006" text,
  "2007" text,
  "2008" text,
  "2009" text,
  "2010" text,
  "2011" text
);
SELECT "tournament" FROM "doubles_performance_timeline" WHERE "2001"='a' AND "2006"='a';