Oldest DOI in CrossRef
With the addition of JSTOR content it appears that the oldest article in CrossRef is:
Transactions of the American Philosophical Society, Vol. 1, Jan. 1, 1769 - Jan. 1, 1771, pp. 293-300. doi:10.2307/1005040 URL:http://dx.doi.org/10.2307/1005040.
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