### Database Schema:
CREATE TABLE cites (
	cited_paper_id	TEXT	NOT NULL	PRIMARY KEY,
	citing_paper_id	TEXT	NOT NULL	PRIMARY KEY
);

CREATE TABLE content (
	paper_id	TEXT	NOT NULL	PRIMARY KEY,
	word_cited_id	TEXT	NOT NULL	PRIMARY KEY,
	foreign key (paper_id) references paper (paper_id)
);

CREATE TABLE paper (
	paper_id	TEXT	NOT NULL	PRIMARY KEY,
	class_label	TEXT	NOT NULL
);

### User's Query:
List all words cited in the AI class label.

### Extra Knowledge:

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'