1. Ingram, J.E.: Spectroscopy at Radio and Microwave Frequencies, 2nd Ed., London: Butterworth 1967
2. Klesper, E., Sielaff, G. in Hummel, D.O. (ed.): Polymer Spectroscopy, Weinheim: Verlag Chemie 1974, p. 189
3. Bovey, F.A.: High Resolution NMR of Macromolecules, New York: Academic Press 1972
4. Levins, J.N.: Molecular Spectroscopy, New York: Wiley 1975, p. 331
5. Tables of chemical shifts are reproduced in recent editions of the Handbook of Chemistry and Physics, CRC Press