Lehrmann, D. J.; Ramezan, J.; Bowring, S.A.; et al. (December 2006). "Timing of recovery from the end-Permian extinction: Geochronologic and biostratigraphic constraints from south China". Geology. 34 (12): 1053–56. Bibcode:2006Geo....34.1053L. doi:10.1130/G22827A.1.
Berner, R, et al., 2003, Phanerozoic atmospheric oxygen, Annu. Rev. Earth Planet. Sci., V, 31, p. 105–34. See the graph near the bottom of the webpage Phanerozoic EonArchived 27 April 2013 at the Wayback Machine
Lehrmann, D. J.; Ramezan, J.; Bowring, S.A.; et al. (December 2006). "Timing of recovery from the end-Permian extinction: Geochronologic and biostratigraphic constraints from south China". Geology. 34 (12): 1053–56. Bibcode:2006Geo....34.1053L. doi:10.1130/G22827A.1.
hathitrust.org
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See:
Phillips, John (1840). "Palæozoic series". Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge. Vol. 17. London: Charles Knight and Co. pp. 153–54.
Bergman N. M., Lenton T. M., Watson A. J. 2004 COPSE: a new model of biogeochemical cycling over Phanaerozoic time. Am. J. Sci. 304, 397–437. See the dashed line in Fig. 1 of Atmospheric oxygen level and the evolution of insect body size by Jon F. Harrison, Alexander Kaiser and John M. VandenBrooks
Berner, R, et al., 2003, Phanerozoic atmospheric oxygen, Annu. Rev. Earth Planet. Sci., V, 31, p. 105–34. See the graph near the bottom of the webpage Phanerozoic EonArchived 27 April 2013 at the Wayback Machine