Scholars of the 19th century tended to interpret these titles as the names of distinct works covering separate voyages; for example, Smith's "Dictionary of Greek and Roman Biography and Mythology" hypothesizes a voyage to Britain and Thule written about in "Ocean" and another from Cadiz to the Don River, written about in "Sail Around". As is common with ancient texts, multiple titles may represent a single source, for example, if a title refers to a section rather than the whole. Presently periplus is recognized as a genre of navigational literature. Mainstream consensus is that there was only one work, "on the Ocean", which was based on a periplus.