H. Saleh, N. Nurdyansyah, F. N. Hasanah, H. E. Rudyanto, and M. Mu’alimin, “Application of Classroom Response Systems (CRS): Study to Measure Student Learning Outcome”, Int. J. Emerg. Technol. Learn., vol. 14, no. 14, pp. pp. 132–142, Jul. 2019.