Boynton, W. V., d'Uston, C., Arnold, J. R., Trombka, J. I., Feldman, W. C., Mitrofanov, I., et al. (1999). Scientific investigations on the elemental composition of Mars by means of the Mars Surveyor 2001 gamma-ray spectrometer. In Lunar and Planetary Science XXX. Houston: Lunar and Planetary Institute.