Roston, G. D., and M. S. Helmi. “The Impact Parameters of the Broadening and Shift of Spectral Lines”. Biological Sciences - PJSIR 48, no. 2 (April 25, 2005): 75–80. Accessed July 22, 2024. https://v2.pjsir.org/index.php/biological-sciences/article/view/1330.