DEVELOPMENT OF LKPD MODEL DISCOVERY LEARNING ACTIVITY ORIENTED CRITICAL THINKING ON VIBRATION MATERIALS, WAVES, AND SOUND FOR LEARNING IPA CLASS VIII IN JUNIOR HIGH SCHOOL 13 PADANG. universe [Internet]. 2021 Jun. 16 [cited 2026 Aug. 20];2(1):18-24. Available from: http://universe.ppj.unp.ac.id/index.php/universe/article/view/34