Rahmawati, F. and Muhtadi, A. 2019. A Development of Integrative Thematic Textbook with Problem-Based Learning to Improve the Critical-Thinking Ability of Elementary Students at Grade IV. KnE Social Sciences. 3, 17 (Jun. 2019), 334–341. DOI:https://doi.org/10.18502/kss.v3i17.4655.