1. W.A. MAYER, Erdöl-Kohle—Erdgas—Petrochem. Verein. Brennstoff-Chemie, 24 (1971) 415.
2. J.F. BOYLE, ASTM STP 531, 1973, 191.
3. H. A. BRAIER, J. EPPOLITO, in The Role of Trace Metals in Petroleum, T.F. YEN (Ed.), Ann Arbor Science Publ., Michigan, 1975, p. 65.
4. S. BANERJEE, B.P. SINHA, R.K. DUTTA, Talanta, 22 (1975) 689.
5. G.L. EVERETT, T.S. WEST, R.W. WILLIAMS, Anal. Chim. Acta, 66 (1973) 301.