1. Allen, W. M. 1950. A simple method for analyzing complicated absorption curves, of use in the colorimetric determination of urinary steroids. J. clin. Endocr. 10. 71–83.
2. Bloom, D. S., Jacobson, E. D. & Grossman, M. I. 1967. Validation of dilution indicators in the stomach. Gastroenterology 52, 205–210.
3. Hydén, S. 1955. A turbidimetric method for the determination of higher polyethylene glycols in biological materials. Ann. roy. Agric. Coll. Sweden 22, 139–145.
4. Ivey, K. J. & Schedl, H. P. 1970. Gastric nonabsorbable indicators for studies in man. Gastroenterology 59, 234–239.
5. Linder, A. E., Cohen, N., Dreiling, D. A. & lanowitz, H. D. 1963. Electrolyte changes in the human stomach following instillation of acid solutions. Clin. Sci. 26, 195–205.