Citation: A. Simonetti et al., TRACE-ELEMENT AND RARE-EARTH-ELEMENT GEOCHEMISTRY OF THE JUNE 1993 NATROCARBONATITE LAVAS, OLDOINYO-LENGAI (TANZANIA) - IMPLICATIONS FOR THE ORIGIN OF CARBONATITE MAGMAS, Journal of volcanology and geothermal research, 75(1-2), 1997, pp. 89-106