U. S. Srivastava and P. D. Srivastava, “On the Hydrogen-Ion Concentration in the Alimentary Canal of Certain Orthopteroid Insects”., contrib.entomol., vol. 6, no. 5-6, pp. 493–498, Dec. 1956, doi: 10.21248/contrib.entomol.6.5-6.493-498.