Apsari, Sofia Rieni, and R. Hermawan. “ANALISIS EKONOMI PRODUKSI KEDELAI HITAM DI KECAMATAN PLAYEN KABUPATEN GUNUNGKIDUL (BLACK SOYBEAN PRODUCTION ECONOMIC ANALYSIS IN PLAYEN SUB-DISTRIC, GUNUNG KIDUL)”. Jurnal Ilmu-Ilmu Pertanian, vol. 5, no. 1, July 2009, pp. 38-44, https://jiip.polbangtanyoma.ac.id/index.php/jiip/article/view/207.