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Adam served as the Papal missionary in Persia from 1314 to 1317, one of six Dominicans sent by Pope John XXII to Persia. However, it is now thought that Adam was probably in Persia before 1314, during the pontificate of Pope Clement V.
On 26 October 1324, he was elected Archbishop of Antivari in the Old Doclea. He after a disagreement with the Pope, Adam stepped down as Archbishop in 1341. Also he wrote about the Scestani and kathars history about this area.
A 1332 document written in Latin that may have be authored by Guillaume Adam (although it may also have been the work of Brocardus Monacus (Frère Brochard)) testifies the existence of written Albanian at that time, although no records of written Albanian have been retrieved from before the 15th century. Though the reference to the existence of the language is clear, that to writing in Albanian is ambiguous. It cannot be said for certain whether the author meant Albanian-language books written in Latin script or simply books written in Latin.
- De modo Sarracenos extirpandi (ca. 1316-1317)
- Directorium ad Passagium Faciendum per Phillippum regem Franciae in terram santam anno 1332 (1332)
- Arbor caritatis
- Elsie, Robert (2003). Early Albania: a reader of historical texts, 11th-17th centuries. Harrassowitz. pp. 28–30. ISBN 978-3-447-04783-8.