 A key part of Severin's thesis is that whilst the text of the "Odyssey" contains many place names to the east and south of Greece, there are very few identifiable references to places to the west.As a result, he questions whether the western Mediterranean was known about at the time the original legends emerged (which he estimated to be some centuries before Homer composed the poem) and so consequently he doubted whether the stories had their origins there.In addition he noted that the Acheron is marked on the map, but traditionally ignored, whilst in the "Argonautica" of Apollonius of Rhodes the Argonauts' home voyage took them into the Adriatic and Ionian Seas, corresponding to a north west Greek location for many of the later adventures.