1. Chou, C. L. Fractionation of siderophile elements in the Earth's upper mantle. Proc. Lunar Planet. Sci. Conf. 9, 219–230 (1978).
2. Jagoutz, E. et al. The abundances of major, minor and trace elements in the Earth's mantle as derived from primitive ultramafic nodules. Proc. Lunar Planet. Sci. Conf. 2, 2031–2050 (1979).
3. Meisel, T., Walker, R. J. & Morgan, J. W. The osmium isotopic composition of the primitive upper mantle. Nature 383, 517–520 (1996).
4. Palme, H. & Beer, H. in Astronomy and Astrophysics (ed. Voigt, H. H.) 196–221 (Springer, Berlin, (1993)).
5. Jochum, K. P. Rhodium and other platinum-group elements in carbonaceous chondrites. Geochim. Cosmochim. Acta 60, 3353–3357 (1996).