Umar B, Jatmiko B, Raharjo R. DEVELOPMENT OF NATURAL SCIENCE LEARNING INSTRUMENTS WITH CONTEXTUAL APPROACH USING PROBLEM SOLVING MODEL TO IMPROVE CRITICAL THINKING SKILL OF JUNIOR HIGH SCHOOL STUDENTS. J. penelitian. pendidik. sains [Internet]. 2018Jun.26 [cited 2024May4];7(2):1501-6. Available from: https://journal.unesa.ac.id/index.php/jpps/article/view/2931