R. Kierepko., S.K. Sahooa., M. Hosoda., S. Tokonami., A. Sorimachid., E. Kim., M. Ohno.,238Pu/(239+240)Pu activity ratio as an indicator of Pu originating from the FDNPP accident in the terrestrial environment of Fukushima Prefecture.Journal of Environmental Radioactivity  196   133 – 140,   (2019).