Hendriana, H., Johanto, T., & Sumarmo, U. (2018). The role of problem-based learning to improve students' mathematical problem-solving ability and self confidence. Journal on Mathematics Education, 9(2), 291--299. https://doi.org/10.22342/jme.9.2.5394.291-300
Molinini, R. M., Koziol, N. A., Tripathi, T., Harbourne, R. T., McCoy, S. W., Lobo, M. A., Bovaird, J., & Dusing, S. C. (2021). Measuring Early Problem-Solving in Young Children with Motor Delays: A Validation Study. Physical and Occupational Therapy in Pediatrics, 41(4), 390--409. https://doi.org/10.1080/01942638.2020.1865501
Siagian, M. V, Saragih, S., & Sinaga, B. (2019). Development of Learning Materials Based on Realistic Mathematics Education Approach to Improve Students' Mathematical Problem Solving Ability and Self-Efficacy. International Electronic Journal of Mathematics Education, 14(2), 331--340.
van Velzen, J. H. (2017). Complex problem solving in L1 education: Senior high school students' knowledge of the language problem-solving process. Journal of Educational Research, 110(6), 634--641. https://doi.org/10.1080/00220671.2016.1171198
