Columbia subject headings:
Batman (Fictitious character)--Comic books, strips, etc.
Extraterrestrial beings--Comic books, strips, etc.
Graphic novels.
Human-alien encounters--Comic books, strips, etc.
Superman (Fictitious character)--Comic books, strips, etc.
Harvard subject headings:
Batman (Fictitious character)--Comic books, strips, etc.
Science fiction comic books, strips, etc.
Superman (Fictitious character)--Comic books, strips, etc.
Princeton subject headings: