1. Phthalsäureanhydrid und Seine Verwendung
2. Verfahren zur Darstellung von Phtalsäure und Sulfophtalsäure aus Naphthalin oder Naphthalinderivaten. DE91202 filed 31 March 1896.
3. Wohl A.Verfahren zur Herstellung von Phthalsäureanhydrid. DE379822 filed 29 June 1916.
4. Process for oxidizing aromatic hydrocarbons having a plurality of side chains or consisting of a plurality of rings and the lower oxidation products of such hydrocarbons. GB119518 (A) filed 1 October 1917 and issued 1 October 1918.
5. Pongratz A.Process for producing phthalic anhydride. US2 157 965 (A) filed 27 October 1938 and issued 9 May 1939.