Gratisdata:Property proposal/PMCID

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Motivation
Just as the description says, identifier for a scientific work issued by PubMed Central (without "PMC" prefix), this one would be without PMC prefix and would somehow easy adding IDs of journals Ugochimobi 16:18, 31 January 2022 (UTC)


 * ✅ Ugochimobi 15:48, 10 February 2022 (UTC)