Feynman, R. P.; de Hoffmann, F. & Serber, R. Dispersion of the Neutron Emission in U$sup 235$ Fission, report, January 1, 1955; (https://digital.library.unt.edu/ark:/67531/metadc1026050/m1/1/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .