See Quran.
Quran – Islam’s holy book as taught by Prophet Muhammad. The preferred spelling is Quran, with the spelling Koran only to be used if preferred by a specific organisation or in a specific tile or name.
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Reuters: Use Koran for the Muslim holy book. (AP uses Quran). Use alternate spellings only if preferred by a specific organization as part of a name or title.
AP: Use Quran in all references except when preferred by an organization or in a specific title or name. See Quran.