1. L. Nicolini:Nature,170, 938 (1952).
2. L. Nicolini:Lettre sous plis cachetés (November 29th, 1952).
3. Italian Patent 7592, (Aug. 9th, 1951).
4. L. Nicolini:Rendiconti A.E.I., Bellagio, 31 October 1954, n. 176.
5. L. Nicolini:Minutes of the Faculty of Engineering,70, no. 50 (1952).