<Li> Historia da Ethiopia, Pedro Páez (aka Pero Pais), Portugal, 1620 </Li> <Dl> <Dd> A Jesuit missionary who was sent from Goa to Ethiopia in 1589 and remained in the area until his death in 1622 . Credited with being the first European to view the source of the Blue Nile which he describes in this volume . </Dd> </Dl> <Dd> A Jesuit missionary who was sent from Goa to Ethiopia in 1589 and remained in the area until his death in 1622 . Credited with being the first European to view the source of the Blue Nile which he describes in this volume . </Dd> <Ul> <Li> Voyage historique d'Abissinie, Jerónimo Lobo (aka Girolamo Lobo), Piero Matini, Firenze; 1693 </Li> </Ul>

How many tributaries does the river nile have