Hsing, and Silhavy. (1997) 1997. “Function of Conserved Histidine-243 in Phosphatase Activity of EnvZ, the Sensor for Porin Osmoregulation in Escherichia Coli”. J Bacteriol 179 (11): 3729-35. doi:10.1128/jb.179.11.3729-3735.1997. Reference Link