References
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- PENIONZHKEVICH, E. E., G. S. KROK. (1977). Proceedings of the All-Union Poultry Research and Technological Institute, vol. 43, Zagorsk, pp. 24–28.
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- PENIONZHKEVICH, E. E., G. S., KROK. (1978). Proceedings of the XVI World's Poultry Congress, Brazil, XI, 1844–1851.