List all words cited in the AI class label.
SELECT DISTINCT T2.word_cited_id FROM paper AS T1 INNER JOIN content AS T2 ON T1.paper_id = T2.paper_id WHERE T1.class_label = 'AI'
database name:db_id citeseer
cites table cites Cols: cited_paper_id dtype text, citing_paper_id dtype text, 
paper table paper Cols: paper id dtype text, class label dtype text, 
content table content Cols: paper id dtype text, word cited id dtype text, 
