Concentrations and isotope ratios of helium and other noble gases in the Earth's atmosphere during 1978–2011
Brennwald, M. S., Vogel, N., Figura, S., Vollmer, M. K., Langenfelds, R., Steele, L. P., … Kipfer, R. (2013). Concentrations and isotope ratios of helium and other noble gases in the Earth's atmosphere during 1978–2011. Earth and Planetary Sciences Letters, 366, 27-37. https://doi.org/10.1016/j.epsl.2013.01.039