"there was, to our knowledge, no actual, direct estimate of numbers of cells or of neurons in the entire human brain to be cited until 2009. A reasonable approximation was provided by Williams and Herrup (1988), from the compilation of partial numbers in the literature. These authors estimated the number of neurons in the human brain at about 85 billion [...] With more recent estimates of 21-26 billion neurons in the cerebral cortex (Pelvig et al., 2008 ) and 101 billion neurons in the cerebellum (Andersen et al., 1992 ), however, the total number of neurons in the human brain would increase to over 120 billion neurons." Suzana Herculano-Houzel,
"The human brain in numbers: a linearly scaled-up primate brain", Front. Hum. Neurosci., 09 November 2009 (dx.doi.org/10.3389/neuro.09.031.2009).
«Earth microbes on the moon». Science@Nasa. 1 de septiembre de 1998. Archivado desde el original el 1 de junio de 2012. Consultado el 2 de noviembre de 2010.
"While estimates among different experts vary, an acceptable range is between 100 billion and 200 billion galaxies, Mario Livio, an astrophysicist at the Space Telescope Science Institute in Baltimore, told Space.com."
Elizabeth Howell,, How Many Galaxies Are There?, Space.com, 1 April 1, 2014.
«Earth microbes on the moon». Science@Nasa. 1 de septiembre de 1998. Archivado desde el original el 1 de junio de 2012. Consultado el 2 de noviembre de 2010.
