Solve the following sql problem:
In the papers classified as ML, how many cited butz01algorithmic?

Schema:
SCHEMA:
- Table: cites
  - Column: cited_paper_id
    - Samples: [100157, 100157, 100157, 100157, 100157]
  - Column: citing_paper_id
    - Samples: [100157, 364207, 38848, bradshaw97introduction, bylund99coordinating]
- Table: paper
  - Column: paper_id
    - Samples: [100157, 100598, 101570, 10227, 102637]
  - Column: class_label
    - Samples: [Agents, IR, ML, ML, AI]
- Table: content
  - Column: paper_id
    - Samples: [100157, 100157, 100157, 100157, 100157]
  - Column: word_cited_id
    - Samples: [word1163, word1509, word1614, word1642, word1663]

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'