1. G.W. MONIER-WILLIAMS, Trace Elements in Food, (1949), Chapman and Hall, London.
2. W. SLAVIN, Atomic Absorption Newsletter, Perkin-Elmer Corp.4, 330 (1965).
3. T.T. GORSUCH, Analyst,84, 135 (1959).
4. K.T. JOSEPH, V.K. PANDAY, S.J. RAUT and S.D. SOMAN, Atomic Absorption Newsletter, Perkin-Elmer Corp.7, 25 (1968).
5. Official Methods of Analysis, 10th Ed., Association of Official Agricultural Chemists, Washington, D.C. (1965), sec, 23,002.