Columbia subject headings:
Pliny, the Younger--Correspondence.
Pliny, the Younger--Criticism and interpretation.
Pliny, the Younger. Epistularum libri IX.
Harvard subject headings:
Pliny, the Younger--Criticism and interpretation.
Pliny, the Younger. Correspondence.
Pliny, the Younger. Epistularum libri IX.
Princeton subject headings: