Rahman, A. H. B., W. Wasino, and M. Martitah. “Development of Social Studies Learning Module Based on Problem Based Learning With Outdoor Study to Improve Learning Outcomes of 7th Grade Junior High School Kesatrian 1 Students”. JESS (Journal of Educational Social Studies), Vol. 7, no. 2, Sept. 2018, pp. 132-9, http://journal.unnes.ac.id./sju/jess/article/view/25982.