NURHAYATI, A., and L. AMIN LESTARI. “Developing C.O.C (Congklak, Onet & Crossword Puzzle) Game to Motivate Students in Enriching English’ Vocabulary”. RETAIN : Journal of Research in English Language Teaching, Vol. 6, no. 3, Oct. 2018, https://ejournal.unesa.ac.id/index.php/retain/article/view/25810.