Council of Preslav
... that historians believe the 893 Council of Preslav established Old Bulgarian as the official language and Preslav as the capital of the First Bulgarian Empire?
... that historians believe the 893 <b id="mwDN8"><a href="./Council_of_Preslav" id="mwDOA" rel="mw:WikiLink" title="Council of Preslav">Council of Preslav</a></b> established <a href="./History_of_the_Bulgarian_language" id="mwDOE" rel="mw:WikiLink" title="History of the Bulgarian language">Old Bulgarian</a> as the official language and <a class="mw-redirect" href="./Preslav" id="mwDOI" rel="mw:WikiLink" title="Preslav">Preslav</a> as the capital of the <a href="./First_Bulgarian_Empire" id="mwDOM" rel="mw:WikiLink" title="First Bulgarian Empire">First Bulgarian Empire</a>?