1. Spurk, J. H., Ingenieur-Archiv 48, 121–127 (1979).
2. Andrä, R., J. H. Spurk, J. sound and vibration 82, 465–472 (1982).
3. Den Hartog, J. P., Mechanical vibrations 4. ed., McGraw-Hill Book Company (New York-Toronto-London 1956 ).
4. Michele, J., Rheol. Acta 15, 15–22 (1976).
5. Michele, J., Rheol. Acta 17, 42–58 (1978).