Refai, M., S.A Attia, R. M. Salem, and E. M. Al-Dahshan,  "Studies on the pathogenicity and enzymatic activities of Aspergillus fumigatus, A. flavus and A. niger isoated from chickens and their environment.",  Egypt. J. Comp. Path.&Clin.Path. , vol. 17 : 17 , pp. 193-205., 2004.