6Chopra AK, Peterson JW, Chary P, et al. Molecular characteriza- tion of an enterotoxin from Salmonella typhimurium [ J ]. Microb Pathog, 1994, 16(2): 85-98.
7Guarino A, Capano G, Malamisura B, et al. Production of Esche- richia coli STa - like heat - stable enterotoxin by Citrobacter freun- dii isolated from humans[ J]. Clin Microbiology, 1987, 25 ( 1 ) : 110 - 114.