Munfaridah, Imroatul, et al. “Karl Popper’s Falsification Theory of the Determination of the Gregorian Calendar Based on the Book of Risalatul Falakiyah K.H Misbachul Munir”. International Journal Ihya’ ’Ulum Al-Din, vol. 25, no. 2, Dec. 2023, pp. 154-67, doi:10.21580/ihya.25.2.18178.