Bhatia, Anand K. “Excitation of (1s2s) 1S, the Singlet State of Helium Atoms by Positron Impact”. Journal of Atomic, Molecular, Condensed Matter and Nano Physics 12, no. 1 (October 26, 2025). Accessed October 26, 2025. https://www.journals.rgnpublications.com/index.php/jamcnp/article/view/3180.