Wada, M., Kasuya, T., Okada, Y. and Lumawag, E.D. 1999. A compact plasma generator with a Ta hollow cathode. Proceedings of the Samahang Pisika ng Pilipinas, 17(1), SPP-1999-SG-11. URL: https://proceedings.spp-online.org/article/view/SPP-1999-SG-11.