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2. F. F. Nord and G. deStevens: Handbuch der Pflanzenphysiologie (Lignins and Ligni-fication) X, 390–441 (1958).
3. G. deStevens: U.S. Patent 2,882,160, April 14, 1959.
4. G. deStevens: U.S. Patent 2,892,835, June 30, 1959.
5. G. deStevens: U.S. Patent 2,892,836, June 30, 1959.