https://ui.adsabs.harvard.edu/abs/2003Sci...301...84M (Any fulltext)
Münker, C., Pfänder, J. A., Weyer, S., Büchl, A., Kleine, T., & Mezger, K. (2003). Evolution of Planetary Cores and the Earth-Moon System from Nb/Ta Systematics. Science, 301, 84-88. doi:10.1126/science.1084662.