1. M. S. Malkevich, Izv. Akad. Nauk SSSR, Ser. Geofiz., No. 8 (1958).
2. G. I. Marchuk, Numerical Methods for the Design of Nuclear Reactions [in Russian], Atomizdat, Moscow (1958).
3. V. S. Vladimirov, Tr. Mat. Inst. im. V. A. Steklova, LXI (1961).
4. Devaux, Nouv. Rev. Opt.,4, No. 5 (1973).
5. R. Marshak, Phys. Rev.,71 (1947).