Jasechko, S., Perrone, D., Befus, K.M., Bayani Cardenas, M., Ferguson, G., Gleeson, T., Luijendijk, E., McDonnell, J.J., Taylor, R.G., Wada, Y. , & Kirchner, J.W. (2017). Global aquifers dominated by fossil groundwaters but wells vulnerable to modern contamination. Nature Geoscience 10 (6), 425-429. 10.1038/ngeo2943.