Tombaugh, C. W. (1946). „The Search for the Ninth Planet, Pluto“. Astronomical Society of the Pacific Leaflets. 5-jild, № 209. 73–80-bet. Bibcode:1946ASPL....5...73T.
adsabs.harvard.edu
McKim, R. (1995). „Astronomy on Mars Hill“. Journal of the British Astronomical Society. 105-jild. 69–74-bet.