Question: What is the USN 2013 ranking with a BW 2013 ranking less than 1000, a Forbes 2011 ranking larger than 17, and a CNN 2011 ranking less than 13?
SQL: SELECT SUM(usn_2013) FROM table_name_63 WHERE bw_2013 < 1000 AND forbes_2011 > 17 AND cnn_2011 < 13