Trembac, V.V. , Luminaires, Soviet Union Publishing Institute for Energy Technology, Moscow , Leningrad (1958). (The problem dealt with in Section 2 has been solved independently by others, for instance by W. Wolber: see Lichttechnik, 22, 597 (1970)).
2.
Bodmann, H.W. , Lectures on lighting engineering, University Karlsruhe (1969 continued)
