Which player from GER has a transfer window of summer, and a transfer fee of n/a?
CREATE TABLE "transfers_out" (
  "nat" text,
  "name" text,
  "type" text,
  "transfer_window" text,
  "transfer_fee" text
);
SELECT "name" FROM "transfers_out" WHERE "transfer_window"='summer' AND "nat"='ger' AND "transfer_fee"='n/a';