Héctor René Vega-Carrillo., and Celia Torres-Muhech. “Low Energy Neutrons from a $^{239}$PuBe Isotopic Neutron Source Inserted in Moderating Media”. Revista Mexicana De Física, vol. 48, no. 5, Jan. 2002, pp. 405-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3082.