1. Anderson, R. N., Bull. geol. Soc. Am., 83, 2947 (1972).
2. Lister, C. R. B., Geophys. J. R. astr. Soc., 25, 515 (1972).
3. Deffeyes, K. S., in Megatectonics of Continents and Oceans, 194 (Rutgers University Press, New Brunswick, 1970).
4. Palmerson, G., in Iceland and Mid-Ocean Ridges (edit. by Bjornsson, S.), 111 (Visindafélag Islendinga, 1967).
5. Williams, D. L., Von Herzen, R. P., Sclater, J. G., and Anderson, R. N., Geophys. J. R. astr. Soc. (in the press).