-- Database schema
| cites : cited_paper_id [ TEXT ] , citing_paper_id [ TEXT ] | paper : paper_id [ TEXT ] primary_key , class_label [ TEXT ] | content : paper_id [ TEXT ] content.paper_id = paper.paper_id , word_cited_id [ TEXT ] |
-- -- In the papers classified as ML, how many cited butz01algorithmic?

SELECT COUNT(T1.paper_id) FROM paper AS T1 INNER JOIN cites AS T2 ON T1.paper_id = T2.citing_paper_id WHERE T1.class_label = 'ML' AND T2.cited_paper_id = 'butz01algorithmic';