Columbia subject headings:
Geography.
Travel in literature.
Twain, Mark, 1835-1910--Knowledge and learning.
Twain, Mark, 1835-1910--Travel.
Voyages and travels.
Harvard subject headings:
Travel in literature.
Twain, Mark, 1835-1910--Knowledge--Geography.
Twain, Mark, 1835-1910--Travel.
Voyages and travels
Princeton subject headings:
Travel in literature.
Twain, Mark, 1835-1910--Knowledge--Geography.
Twain, Mark, 1835-1910--Travel.
Voyages and travels.