Analysis of information sources in references of the Wikipedia article "Principality of Moscow" in English language version.
But the crucial year was 1326, when [Metropolitan] Peter became a resident of Moscow and began to build his burial vault. On December 20, 1326. Metropolitan Peter died and was buried by one of the bishops in the presence of Ivan I. Due to his residency and burial place, Metropolitan Peter had confirmed Moscow the future haven of the Russian Orthodox Church, although this official transfer would not take place until the reign of Alexis.
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