 Deen consulted with the Basque scholar Julio de Urquijo, and in 1937, Deen published his doctoral thesis on the Basque–Icelandic glossaries.It was called "Glossaria duo vasco-islandica" and written in Latin, though most of the phrases of the glossaries were also translated into German and Spanish.In 1986 Jón Ólafsson's manuscripts were brought back from Denmark to Iceland.