1. A. HONIG, LUDMILA POSPISILOVA-ROTHSCHEINOVA, P. KABLENA, and J. HABARTA, “Commercial Portable Gauges for Radiometric Determination of the Density and Moisture Content of Building Materials—A Comparative Study,” Technical Report Series No. 130, International Atomic Energy Agency (1971).
2. A. M. WEINBERG and E. P. WIGNER, The Physical Theory of Neutron Chain Reactors, University of Chicago Press (1958).