García-Díaz, M. T., W. J. Henney, J. A. López, and T. Doi. “Velocity Structure in the Orion Nebula. II. Emission Line Atlas of Partially Ionized to Fully Ionized Gas”. Revista Mexicana De Astronomía Y Astrofísica, vol. 44, no. 1, June 2012, pp. 181-12, https://journals.unam.mx/index.php/revmexaa/article/view/23757.