The <a href="https://en.wikipedia.org/wiki/First_Council_of_Nicaea" id="mwEQ" rel="mw:WikiLink" title="First Council of Nicaea">First Council of Nicaea</a> is formally opened, starting the first <a href="https://en.wikipedia.org/wiki/Ecumenical_council" id="mwEg" rel="mw:WikiLink" title="Ecumenical council">ecumenical council</a> of the Christian Church.<sup about="#mwt15" class="mw-ref reference" data-mw='{"name":"ref","attrs":{},"body":{"id":"mw-reference-text-cite_note-1"}}' id="cite_ref-1" rel="dc:references" typeof="mw:Extension/ref"><a href="./May_20#cite_note-1" id="mwEw" style="counter-reset: mw-Ref 1;"><span class="mw-reflink-text" id="mwFA">[1]</span></a></sup>
<span class="mw-reference-text" id="mw-reference-text-cite_note-1"><cite about="#mwt12" class="citation book cs1" id="CITEREFvon_Hefele2007">von Hefele, Charles Joseph (2007). Clark, William R. (ed.). <a class="external text" href="https://books.google.com/books?id=6_VJAwAAQBAJ" id="mwBtk" rel="mw:ExtLink nofollow"><i id="mwBto">A History of the Councils of the Church From the Original Documents. Vol. 1: To the Close of the Council of Nicea, A.D. 325</i></a>. Translated by Clark, William R. Eugene, Ore.: Wipf &amp; Stock. p.<span id="mwBts" typeof="mw:Entity"> </span>275. <a class="mw-redirect" href="./ISBN_(identifier)" id="mwBtw" rel="mw:WikiLink" title="ISBN (identifier)">ISBN</a><span id="mwBt0" typeof="mw:Entity"> </span><a href="./Special:BookSources/9781556352478" id="mwBt4" rel="mw:WikiLink" title="Special:BookSources/9781556352478"><bdi id="mwBt8">9781556352478</bdi></a>.</cite><span about="#mwt12" class="Z3988" id="mwBuA" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rft.genre=book&amp;rft.btitle=A+History+of+the+Councils+of+the+Church+From+the+Original+Documents.+Vol.+1%3A+To+the+Close+of+the+Council+of+Nicea%2C+A.D.+325&amp;rft.place=Eugene%2C+Ore.&amp;rft.pages=275&amp;rft.pub=Wipf+%26+Stock&amp;rft.date=2007&amp;rft.isbn=9781556352478&amp;rft.aulast=von+Hefele&amp;rft.aufirst=Charles+Joseph&amp;rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D6_VJAwAAQBAJ&amp;rfr_id=info%3Asid%2Fen.wikipedia.org%3AMay+20"></span></span>