Columbia subject headings:
Twain, Mark, 1835-1910--Criticism and interpretation.
Twain, Mark, 1835-1910--Humor.
Harvard subject headings:
Twain, Mark, 1835-1910--Humor.
Princeton subject headings:
Twain, Mark, 1835-1910--Criticism and interpretation.
Twain, Mark, 1835-1910--Humor.