Ostwald, Wilhelm, "Improvements in the Manufacture of Nitric Acid and Nitrogen Oxides", GB 190200698, published January 9, 1902, issued March 20, 1902
Ostwald, Wilhelm, "Improvements in and relating to the Manufacture of Nitric Acid and Oxides of Nitrogen", GB 190208300, published December 18, 1902, issued February 26, 1903