1. K. PRESTON JR.: Proc. IEEE, 60-10, 1216-31, (1972).
2. M. P. PETROV: Acta Politechnica Scandinavica, Ph 149, Vol. 1, 43 (1985).
3. H. C. ANDREWS: Computer Techniques in Image Processing, Academic Press, New York, 31–54 (1970).
4. B. R. FRIEDEN: Image Enhancement and Restauration. In: Picture Processing and Digital Filtering (Ed. T. S. Huang) Berlin: Springer, 181 (1975).
5. P.J.S. HUTZLER: Optical Filtering Techniques in Digital Image Enhancement. IEEE Computer Society Press: Proc. 7ICPR 2, 899 - 901 (1984)