Kharisna F, Amini R. Validity of Kvisoft Flipbook Maker-Assisted PjBL-Based E-books for Elementary Schools. J. Obs. J. Pendidik. Anak Usia Dini [Internet]. 2023 Mar. 27 [cited 2026 Nov. 5];7(2):1809-17. Available from: https://mail.obsesi.or.id/index.php/obsesi/article/view/4205