Pytheas described his travels in a work that has not survived; only excerpts remain, quoted or paraphrased by later authors, most familiarly in Strabo's "Geographica", Pliny's "Natural History" and passages in Diodorus of Sicily's history. Most of the ancients, including the first two just mentioned, refer to his work by his name: "Pytheas says …" Two late writers give titles: the astronomical author Geminus of Rhodes mentions ("ta peri tou Okeanou"), literally "things about the Ocean", sometimes translated as "Description of the Ocean", "On the Ocean" or "Ocean"; Marcianus, the scholiast on Apollonius of Rhodes, mentions ("periodos gēs"), a "trip around the earth" or περίπλους ("periplous"), "sail around".