1) K. F. LAGLER, J. E. BARDACH, R. R. MILLER, and D. R. M. PASSINO: Ichthyology, 2nd ed., Wiley and Sons, New York, 1977, pp. 117-122.
2) V. R. PROTASOV: Vision and Near Orientation of Fish (Translated from Russian), Israel Program for Scientific Translations, Jerusalem, 1970, pp. 87-93.
3) T. RADEDÄTER and A. FERNÖ: Behavioural Processes, 4, 5-13 (1979).