How many papers were cited by schmidt99advanced cited word3555?
paper cited by refers to citing_paper_id; citing_paper_id = 'schmidt99advanced';
SELECT COUNT(T2.paper_id) FROM cites AS T1 INNER JOIN content AS T2 ON T1.cited_paper_id = T2.paper_id WHERE T1.citing_paper_id = 'schmidt99advanced' AND T2.word_cited_id = 'word3555'