Schubert, M., Freyer, K., Treutler, H. C., & Weiss, H. (2002). Using radon-222 in soil gas as an indicator of subsurface contamination by non-aqueous phase-liquids (NAPLs). Geofísica Internacional, 41(4), 433–437. https://doi.org/10.22201/igeof.00167169p.2002.41.4.491