Nevertheless, it is the contention of this paper … [four-color theorem] does drive a wedge between the criteria of surveyability and … 4CT, nor is there likely to be one. … surveyed, what is presented in their published work, … results of certain computer runs or, as we … is ultimately a report on a successful experiment. … grounds that are in part empirical. … [p. 263] after the 4CT, formal proofs cannot continue …
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