1. 1) R. T. Niest : J. Photogr. Sci., 10,188 (1962)
2. 2) V. L. Wagner, J. : Image Technol., 15, 5/6 14 (1973)
3. 3) D. Chenevert : ibid., 15, 5/6 18 (1973)
4. 4) A. J. Batschin et al. : Fotogr. Kinemotogr., 15,291 (1970)
5. 5) H. Jonkeer, et al. : J. Photogr. Sci., 19, 96 (1971), 20, 53 (1972), Photogr. Sci. Eng., 13, 1, 33, 38, 45 (1969)