Purwaningsih, S. (2020) “Ground State Energy of the Helium Using Variational Methods on Trial Wave Functions”, International Journal of Sciences: Basic and Applied Research (IJSBAR), 54(4), pp. 233–241. Available at: https://www.gssrr.org/JournalOfBasicAndApplied/article/view/11800 (Accessed: 18 September 2025).