1. Shiba K, Sueyoshi T, Sato A, Kubodera S, Tsubota M. Photographic emulsion containing optically dye-sensitized silver halide grains of less than 0.2 micron. US Pat 3,706,566; 1972.
2. Sato A, Shiba K, Hinata M. Spectrally sensitized photographic silver halide emulsion. US Pat 3,770,440; 1973.
3. Nakazawa Y, Nakamura Y, Sueyoshi T, Sato A. Fine grain silver halide photographic emulsion containing hemicyanine sensitizing dye. US Pat 3,788,859; 1974.