Abdjul, T., and N. Ntobuo. “Developing Device of Learning Based on Virtual Laboratory through Phet Simulation for Physics Lesson With Sound Material”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 39, no. 2, June 2018, pp. 105-1, https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/9002.