1. Limitations in the use of color indicators in gastric analysis, Am;Berk;J. Digest. Dis.,1942
2. Michaelis, L.: Quoted by Hollander, F. and Penner, A.3
3. History and development of gastric analysis procedure, Am;Hollander;J. Digest. Dis., 5: 786,1939
4. Determination of the acidity of gastric contents; II;Shohl;The colorimetric determination of free hydrochloric acid, Bull. Johns Hopkins Hosp.,1920
5. Clinical Laboratory Diagnosis;Levinson,1946