Bito, Nursiya, et al. “The Development of Character Building-Based Two-Dimensional Shapes Multimedia on Junior High School Students in Gorontalo Province, Indonesia”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 48, no. 1, Aug. 2019, pp. 115-2, https://gssrr.org/JournalOfBasicAndApplied/article/view/10200.