https://sites.google.com/educarex.es/commercium-epistularum/quomodo/summa
Commercium Epistularum - SUMMA
commerciumsumma
https://patrologia.narod.ru/nationes/pliniuss/index.htm
C. Plini Caecili Secundi epistularum libri novem
Plinius, Epistularum ad Traianum liber, Panegyricus, Keil
cplinilibrinovem