1. E. Krestel, Physiologie des Sehens, in: Bildgebende Systeme für die medizinische Diagnostik, Verlag Siemens AG, Berlin-München, (1980).
2. M. E. Bernadino, J. L. Thomas, G. B. Mayes, An Initial Experience with Post- Data Processing in Hepatic Sonography, American Journal Radiology, 136(3):521(1981).
3. D. Nicholas, Pre-and Postprocessing of images held on temporary storage devices, in: Medical Ultrasonic Images, C. R. Hill, A. Kratochwil, ed., Exerpta International Congress Series No.541, Amsterdam-Oxford-Princeton(1981).
4. J. M. Thijssen, B. J. Osterveld, R. F. Wagner, Gray Level Transforms and Lesion Detectability in Echographic Images, Ultrasonic Imaging, 10: 171 (1988).
5. A. Rosenfeld, A. C. Kak, in: Digital Picture Processing, Academic Press, New York- San Francisco-London (1976).