1. Dunn J. S. (1934) Journal of the Institute of Metals 46:25
2. Frohlich K. W. (1936) Zeitschrift for Metallkunde 28:368
3. Price L. E., Thomas G. J. (1938) Journal of the Institute of Metals 63:21
4. Dennison J. P., Preece A. (1952) Journal of the Institute of Metals 81:229
5. Blade J. C., Preece A. (1959) Journal of the Institute of Metals 88:427