Duklja was a medieval Serb state which roughly encompassed the territories of present-day southeastern Montenegro, from the Bay of Kotor in the west to the Bojana river in the east, and to the sources of the Zeta and Morača rivers in the north. It was first mentioned in the 10th century Byzantine chronicles, which remain the most important sources on Duklja's history in the 11th and 12th century: John Skylitzes, Skylitzes Continuatus, Katakalon Kekaumenos and Anna Komnene in her work "The Alexiad". Constantine VII Porphyrogenitus doesn't give any data on the rulers of Duklja. A lead seal from the 9th or the 10th century points to a certain "Prince Peter of Duklja" but there are no other data on him.