Hubble, Edwin." Scientists, Mathematicians & Inventors: Lives & Legacies: An Encyclopedia Of People Who Changed The World (Bio Ref Bank) (1999): Biography Reference Bank (H.W. Wilson). Web. 16 Apr. 2013.
Datnow, Claire L. "Edwin Hubble: Discoverer Of Galaxies." (n.d.): Biography Reference Bank (H.W. Wilson). Web. 25 Apr. 2013.
Edwin Powell Hubble." (2005): Biography Reference Bank (H.W. Wilson). Web. 25 Apr. 2013.
Michael Chenoweth
Datnow, Claire L. "Edwin Hubble: Discoverer Of Galaxies." (n.d.): Biography Reference Bank (H.W. Wilson). Web. 25 Apr. 2013.
Edwin Powell Hubble." (2005): Biography Reference Bank (H.W. Wilson). Web. 25 Apr. 2013.
Michael Chenoweth