● Hadley P,Elkins MW,Caldwell DW (1918). The Colon-Typhoid Intermediates as Causative Agents of Disease in Birds: I. The Para-typhoid Bacteria. Bull. - Agric. Exp. Sta. R. I. 174, 1-216.
● Brenner DJ,Farmer III JJ,Fanning GR,Steigerwalt AG,Klykken P,Wathen HG,Hickman FW,Ewing WH (1978). Deoxyribonucleic acid relatedness in species of Proteus and Providencia. Int. J. Syst. Bacteriol. 28, 269-282.