1. H. J. Jordan, First Report on Viscosity and Plasticity, p. 214, 221 (Amsterdam: Noord-Hollandsche Uitg.-Maatsch., 1935).
2. H. H. Pfeiffer, Physics, 7, 302 (1936).
3. Pfeiffer, Cytologia, 6, 329 (1935). Protoplasma, 26, 372 (1936).
4. W. Seifriz, Protoplasm, 246, 261. (New York and London: McGraw-Hill, 1936.)
5. H. Pfeiffer, Protoplasma, 23, 210 (1935).