Browne, C. A. (1941). "Bernhard Tollens (1841–1918) and Some American Students of his School of Agricultural Chemistry". Journal of Chemical Education. 19 (6): 253–259. Bibcode:1942JChEd..19..253B. doi:10.1021/ed019p253.
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Browne, C. A. (1941). "Bernhard Tollens (1841–1918) and Some American Students of his School of Agricultural Chemistry". Journal of Chemical Education. 19 (6): 253–259. Bibcode:1942JChEd..19..253B. doi:10.1021/ed019p253.