What is the most cited word? How many papers was that word cited in?
most cited word refers to max(count(word_cited_id);
SELECT word_cited_id, COUNT(paper_id) FROM content GROUP BY word_cited_id ORDER BY COUNT(word_cited_id) DESC LIMIT 1
CREATE TABLE cites
(
    cited_paper_id  TEXT not null,
    citing_paper_id TEXT not null,
    primary key (cited_paper_id, citing_paper_id)
);
CREATE TABLE paper
(
    paper_id    TEXT  not null
        primary key,
    class_label TEXT not null
);
CREATE TABLE content
(
    paper_id     TEXT not null,
    word_cited_id TEXT not null,
    primary key (paper_id, word_cited_id),
    foreign key (paper_id) references paper(paper_id)
);
