1. C. Appert eR. Cabarat:Compt. Rend.,228, 490 (1949).
2. C. Appert eR. Cabarat:Compt. Rend.,228, 1871 (1949).
3. O. v. Auwers:Ann. der Phys. 17, 83 (1933).
4. P. G. Bordoni:Atti II Convegno Nazionale della Assoc. It. di Metallurgia (1948).
5. P. G. Bordoni:Ric. Scient.,19, 851 (1949).