1. J. F. Fredrick, Phiton (Buenos-Aires),17, 147 (1961), C.A.57, 3730 d (1962).
2. L. C. Mitchell, J. Assoc. Offic. Agr. Chemists,44, 643 (1961).
3. H. T. Gordon, W. W. Thornburg, L. N. Werum, J. Chromatogr.9, 44 (1962).
4. F. Schindler, F. Kuffner, Monatsh. Chem.94, 252 (1963).
5. A. Cee, M. Adamek, Sb. Ved. Praci, Vysoka Skola Chem. Technol., Pardubice,17, 5 (1968), C.A. 71, 56483t (1969).