- Levels of nitrite, nitrate, N-nitroso compounds, ascorbic acid and total bile acids in gastric juice of patients with and without precancerous conditions of the stomach. Sobala, G.M., Pignatelli, B., Schorah, C.J., Bartsch, H., Sanderson, M., Dixon, M.F., Shires, S., King, R.F., Axon, A.T. Carcinogenesis (1991)