1. Delmas, R. J., Ascencio, J.-M. & Legrand, M. Nature 284, 155–157 (1980).
2. Neftel, A., Oeschger, H., Schwander, J., Stauffer, B. & Zumbrunn, R. Nature 295, 220–223 (1982).
3. Stauffer, B., Hofer, H., Oeschger, H., Schwander, J. & Siegenthaler, U. Ann. Glaciol. (in the press).
4. Langway, C. C. Jr Physics of the Movement of the Ice, Chamonix (IUGG Meet., IAHS Publ. No. 47, 336–349, 1958).
5. Raynaud, D. & Lebel, B. Nature 281, 289–291 (1979).