Which party is associated with a leader who began his tenure on June 13, 2007?
CREATE TABLE "list_of_negotiation_leaders" (
  "from" text,
  "until" text,
  "name" text,
  "party" text,
  "function" text
);
SELECT "party" FROM "list_of_negotiation_leaders" WHERE "from"='june 13, 2007';