1. Green, M. (1921), J. Franklin Inst., 192, 657.
2. Dunn, EJ. (1930), Ind. Engng. Chem., analyt. Edn, 2, 59.
3. Orr, C. and Dallevalle, J.M. (1959), Fine Particle Measurement, Macmillan, NY.
4. Irani, R.R. and Callis, C.F. (1963), Particle Size, Wiley, NY.
5. Harwood, M.G. (1954), B.J. appl. Phys. suppl. 3, S193.