Table schema:
CREATE TABLE table_name_15 (name VARCHAR, moving_from VARCHAR, transfer_window VARCHAR, transfer_fee VARCHAR)

Question: What is the name of the player with a transfer window in summer, an undisclosed transfer fee, and is moving from brussels?
SQL: SELECT name FROM table_name_15 WHERE transfer_window = "summer" AND transfer_fee = "undisclosed" AND moving_from = "brussels"