Columbia subject headings:
Ethics.
Plato. Protagoras.
Protagoras.
Socrates.
Sophists (Greek philosophy)
Harvard subject headings:
Ethics--Early works to 1800
Plato. Protagoras.
Protagoras
Socrates.
Sophists (Greek philosophy)
Princeton subject headings:
Ethics.
Plato. Protagoras.
Protagoras.
Socrates.
Sophists (Greek philosophy)