Tài liệu tham khảo

WikiPedia: J. Allen Hynek http://www.dios.com.ar/notas1/biografias/ufologos/... http://badufos.blogspot.com/2011/12/new-historical... http://www.debunker.com/historical/HynekForgetsHis... http://www.saturdaynightuforia.com/html/articles/a... http://findingaids.library.northwestern.edu/catalo... http://catalogo.bne.es/uhtbin/authoritybrowse.cgi?... http://www.dtic.mil/dtic/tr/fulltext/u2/021921.pdf http://data.bibliotheken.nl/id/thes/p070780676 http://www.cufos.org/org.html http://www.nicap.org/rufo/rufo-03.htm