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Justus von Liebig (1859). “Familiar Letters on Chemistry, in its relation to Physiology, Dietetics, Agriculture, Commerce and Political Economy: Edited by John Blyth”, p.5
Justus von Liebig (1859). “Familiar Letters on Chemistry, in its relation to Physiology, Dietetics, Agriculture, Commerce and Political Economy: Edited by John Blyth”, p.21