KERENTANAN AIRTANAH TERHADAP PENCEMARAN DAERAH IMBUHAN PONOR DI KARST GUNUNG SEWU (STUDI DI DAERAH ALIRAN SUNGAI BAWAD TANAH BRIBIN) = (Ground Water Vulnerability to Contamination of Swallow Holes Recharge Area at Gunun - Perpustakaan UGM, i-lib ([Yogyakarta] : Universitas Gadjah Mada, 2012)