Wikipedia writes "W. T. Tutte conjectured that every snark has the Petersen graph as a minor... In 1999, Neil Robertson, Daniel P. Sanders, Paul Seymour, and Robin Thomas announced a proof of this conjecture.[16] As of 2012, their proof remains largely unpublished.[17]"
These authors have an arxiv paper (submitted 2014, updated November 2015, although the PDF weirldy claims it was updated in September 2018, three years after its publication). This arxiv paper cites no less than three unpublished papers [5,6,8] and which does not appear to have been published itself.
It has been twenty years! (Even twenty-five in the case of citation [6]...). Why is Wikipedia this even listing as a theorem? Is there a general acceptance that this has indeed been proved, and if so, why is none of this getting published?