Samsudi, Samsudi, Eko Supraptono, Sunyoto Sunyoto, and Shohihatur Rohman. “The Implementation of Project-Based Learning in Productive Skill Programs for the Development of 21st Century Vocational School Students ”. KnE Social Sciences 3, no. 18 (July 3, 2019): 470–479. Accessed August 7, 2020. https://knepublishing.com/index.php/KnE-Social/article/view/4738.