1. H. Gross, K. Grodde, and H. Ölu, Kohle, Bd. 38, Nr. 16, S. 419 (1942).
2. G. Spengler and E. K. Jantzen, Fette, Seifen, Anstrichmittel, Bd. 63, Nr. 6, S. 530 (1961).
3. M. M. Kusakov, Methods of determining the physical characteristics of petroleum products, ONTI (1936).
4. M. F. Sukharev, Trudy VNII, part 27, Gostoptekhizdat, 47 (1960).
5. L. Ivanovsky, Ozokerite und verwandte Stoffe, Wien-Leipzig (1939).