Dinges, William D.; Hitchcock, James (1994). «Roman Catholic Traditionalism and Activist Conservatism in the United States». En Marty, Martin E.; Appleby, R. Scott, ed. Fundamentalisms Observed, volumen 1(en inglés). Chicago: The University of Chicago Press. p. 88. ISBN978-0-226-50878-8. Consultado el 13 de diciembre de 2016. «[...] sedevacantist [...] tradicionalists, a highly radicalized fringe element who have refuzed to recognize the popes since Pius XII as valid popes [...] Principal among this sedevacantist segment are priests ordained bishops by the former Vietnamese archbishop Pierre Martin Ngo-Dinh-Thuc.»