1. 2) A. L. BEACH and W.C. GULDMER: Analyt. Chem., 31 (1959), p.1722
2. 3) H. L. HAMMER and R.M. FEWLER: J. Metals, 4 (1952), p.1313
3. 4) M. G. FROHBERG and H. LEYGRAF: Minutes on 3rd Balzers Conference, (1967), p.41
4. 5) G. PAESOLD: Minutes on 2nd Balzers Conference, (1966), p.22
5. 6) C. R. MASSON and M.L. PEARCE: Trans. Met. Soc. AIME, 224 (1962), p.1134