New geochronologic and palaeomagnetic data for the hominid-bearing Hadar Formation of Ethiopia - Aronson, J.L.; Schmitt, T.J.; Walter, R.C.; Taieb, M.; Tiercelin, J.J.; Johanson, D.C.; Naeser, C.; Nairn, A.E.M. (Nature, 1977)