1. E. M. GELBARD, “Applications of Spherical Harmonics Method to Reactor Problems,” WAPD- BT-20, Bettis Atomic Power Laboratory (1960).
2. E. M. GELBARD, “Simplified Spherical Harmonics Equations and Their Use in Shielding Problems,” WAPD-T-1182, Bettis Atomic Power Laboratory (1961).
3. E. M. GELBARD, “Applications of Simplified Spherical Harmonics Equations in Spherical Geometry,” WAPD-TM-294, Bettis Atomic Power Laboratory (1962).
4. Asymptotic Derivation of the MultigroupP1and SimplifiedPNEquations with Anisotropic Scattering
5. Asymptotic and variational derivations of the simplified PN equations