Knoll, Andrew2009-06-291996Knoll, Andrew H. 1996. Breathing room for early animals. Nature 382(6587): 111-112.0028-08361476-4687http://nrs.harvard.edu/urn-3:HUL.InstRepos:3122599Did an increase in atmospheric oxygen concentration some time during the Neoproterozoic era, 1,000 to 543 million years ago, make possible the diversification of multicellular animals?en-US10.1038/382111a0