Maroni, Dizionario di erudizione storico-ecclesiastica (Venice, 1840 sqq.), all of which contain articles on individual popes and subjects connected with the papacy, with bibliographies.
Thus the Gran Sasso and the Maiella are separated by the deep valley of the Aterno, while the Tronto breaks through the range between Monte Vettore and the Pizzo di Sevo.
Its principal tributary is the Sieve, which joins it at Pontassieve, bringing down the waters of the Val di Mugello.
Another lateral rsnge, the Prato Magno, which branches off from the central chain at the Monte Falterona, and separates the upper valley of the Arno from its second basin, rises to 5188 ft.; while a similar branch, called the Alpe di Catenaja, of inferior elevation, divides the upper course of the Arno from that of the Tiber.
Sepolcro and Città di Castello, then between Perugia and Todi to Orte, just below which it receives the Nera.