Susanti, N. E. “ENGARUH ODEL ROBLEM ASED EARNING ERHADAP ASIL ELAJAR EOGERAFI ISWA MA I ABUPATEN ALANG”. PIG (Jurnal endidikan an lmu eografi), vol. 1, no. 1, Sept. 2016, http://ejournal.unikama.ac.id/index.php/JPIG/article/view/1435.