1. Barium titanate as a semiconductor with blocking layers;Heywang;Solid-State Electron.,1961
2. P.W. Haaijman, R.D. Dam, H.A. Klasens, Method of Preparation of Semiconducting Materials, Ger. Pat. No. 929350 (June 1955).
3. Resistivity anomaly in doped barium titanate;Heywang;J. Am. Ceram. Soc.,1964
4. B.M. Kulwicki, PTC Materials Technology 1955–1980, in: L.M. Levinson (Ed.), Advances in Ceramics: Grain Boundary Phenomena in Electronic Ceramics, vol. 1, American Ceramic Society, Columbus, OH, 1981, pp. 138–154.
5. J.S. Reed, Principles of Ceramics Processing, second ed., Wiley, New York, 1995 (Chapter 20).