Cantut, L; Dougan, A; Hemberger, P; Kravenchenko, Gromov, A; Martin, D; Pohl, B et al. Detection of radioactive materials at Astrakhan, article, July 1, 1999; (https://digital.library.unt.edu/ark:/67531/metadc625605/m1/1/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .