1. Anderson, R. M. and Kumar, A., 1977, EMSA Proceedings, 250.
2. Anderson, R. M., Bigelow, W. C., and Lawless, K. R. 1977, EMSA Bulletin. 7, 1, 21 and 1978, ibid, 8, 1, 9.
3. The first reference printed the questionnaire, the second reported the results.
4. Bohg. A., Mirbach, E., and Schneider, L., February, 1978, J. Phys. J. Phys. E. Sci. Instrum. 11, 166.
5. Brown, R. H., Fink, W. L., and Hunter, M. S., 1941, Trans AIME, 143, 115–123.