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2. 2) Polaroid Corp.: Polarized light (1967). U.S.A.
3. 3) Fuji Photographic Film Co., Ltd.: Fuji Photo Handbook: Fuji Filter, p 9 (1971). Japan.
4. 4) Fuji Photographic Film Co., Ltd.:Polaroid Optical Retarder T-166 (1969). U.S.A.
5. 5) S. Tsuboi: Polarizing Microscope (10th Edition), p 166 (1970). Iwanami Shoten, Japan.