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I've removed the phrase in order of first criticality, because I think it was wrong... PLUTO went critical before HIFAR, for example, according to their articles. More research needed, meanwhile better no data than falsehoods. Andrewa 01:41, 11 August 2005 (UTC) reply

As an interim, let's add those first criticality dates we know. Andrewa ( talk) 20:34, 8 February 2014 (UTC) reply