Darma, I. K., Karma, . I. G. M. and 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), pp. 203–213. doi: 10.21744/irjeis.v7n6.1935.