1. States, M.N. (1939), Proc. Am. Soc. Test. Mat., 39, 795.
2. Heywood, H. (1947), Symp. Particle Size Analysis, Inst. Chem. Engrs., 114.
3. Robinson, G.W. (1922), J. Agric. Sci., 12, 3, 306–21.
4. Andreasen, A.H.M. (1928), Kolloid Beith., 27, 405.
5. Andreasen, A.H.M. (1939), Ingen. Vidensk. Skr., 3.