Darma, I. K., Karma, . I. G. M., & Santiana, I. M. A. (2021). Practicality and effectiveness of digital mathematics teaching materials in improving the problem-solving ability for polytechnic students. International Research Journal of Engineering, IT & Scientific Research, 7(6), 203–213. https://doi.org/10.21744/irjeis.v7n6.1935