Strabo’s Geography, Book XVI, 4:26:

https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Strabo/16D*.html

Circa 20 CE is the date that academics who believe that Strabo’s Geography is an accreted work date it to, finished near the end of Strabo’s lifetime: https://www.jstor.org/stable/4477333