Periodicals>Journal Article:  Sagan , Carl and Walker, Russell G. (August 27, 1965), The Infrared Detectability of Dyson Civilizations, American Astronomical Society, Retrieved on 2014-03-16

Source Material [articles.adsabs.harvard.edu]

Unpublished Work>Publication of Limited Circulation:  Sagan , Carl (1994), Advocating science and hope : draft essay, Retrieved on 2014-03-03

Source Material [www.loc.gov]

Unpublished Work>Publication of Limited Circulation:  Sagan , Carl (1982), Alien united nations, Retrieved on 2014-03-03

Source Material [www.loc.gov]

Personal Communications>Personal Letter:  Sagan , Carl (August 2, 1994), Memo to Ann Druyan, George Miller & Linda Obost concerning religious disquiet at prospect of contacting extraterrestrials, Retrieved on 2014-03-03

Source Material [www.loc.gov]

Unpublished Work>Publication of Limited Circulation:  Sagan , Carl (June 21, 1973), Interstellar music : note, Retrieved on 2014-03-03

Source Material [www.loc.gov]

Unpublished Work>Publication of Limited Circulation:  Sagan , Carl (21 December, 1981), Stages of galactic history with respect to extraterrestrial intelligence : note, Retrieved on 2014-03-03

Source Material [www.loc.gov]

Personal Communications>Personal Letter:  Sagan , Carl (January 22, 1992), Letter from Carl Sagan to Carolyn Porco, Library of congress, Retrieved on 2014-03-03

Source Material [www.loc.gov]

Periodicals>Magazine Article:  Sagan , Carl (1995), Wonder and Skepticism, Skeptical Enquirer , (Jan-Feb 1995), 19, No. 1. , Retrieved on 2012-06-21

Books, Brochures, and Chapters>Book:  Sagan , Carl (1985), Can We know the Universe?, The Sacred Beetle and Other Great Essays in Science, Retrieved on 2012-06-21

Source Material [books.google.com]

Books, Brochures, and Chapters>Book:  Sagan , Carl (2000-10-23), Carl Sagan's cosmic connection, Cambridge Univ Pr, Retrieved on 2012-01-01

Source Material [books.google.com]