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2. See, for example, Farr and Eckerson, Contrib. Boyce Thompson Inst., 6, 189 (1934). Farr and Sisson, ibid., 6, 309 (1934).
3. Dippel, Abh. Senckenb. naturf. Ges., 2, 154 (1879). Schmitz, S. B. niederrhein Ges. Nat.-u. Heilk., 37, 200 (1880). Krabbe, J. wiss. Bot., 18, 346 (1887). Wiesner, "Die Elementarstr. usw." (Wien, 1892). Herzog, "Untersuch. der naturaliche u. Künstliche Seiden" (Dresden, 1910).
4. Ruska and Kretscher, Koll. Z., 93, 163 (1940). Marton and McBain, Chem. Products, 1, 16 (1942). Barnes and Burton, Ind. Eng. Chem. (I.E.), 35, 120 (1943). Frey-Wyssling and Muhlethaler, J. Polymer Sci. (1946).
5. Preston, Proc. Leeds Phil. Soc., 2, 185 (1931). Sponsler, Protoptosma, 12, 241 (1931).