Pemisahan Aliran Dasar Bagian Hulu Sungai Bribin pada Aliran Gua Gilap di Karst Gunung Sewu, Gunung Kidul, Yogykarta (Based Saparation of the Bribin River Upstream in Gilap Cave Flowage, Sewu Mountain Karst, Gunung Kidul, Yogyakarta.