1. G. Herrmann, S. Wagener, The Oxide Coated Cathode. Chapman & Hall, London (1951)
2. H.J. Lemmens, M.J. Jansen, R. Loosjes, A new thermionic cathode for heavy loads. Philips Tech. Rev. 11, 341 (1950)
3. H.J. Lemmens, U.S. Patent 2543728, published 27 Feb 1951, priority The Netherlands 26 Nov 1947
4. H. Katz, U.S. Patent 2750527, published 12 June 1956, priority Germany 19 Nov 1951 H. Katz claims earlier priority: French patent specification 903976, publ. 23 Oct 1945, priority Germany 19 Aug 1942
5. H. Katz, Metal capillary cathodes a new type of cathode. Siemens Halske Res. Bull. II, 123-126 (1951)