Petro Doroshenko
...that the Cossack Hetman and the later Muscovite voyevoda Petro Doroshenko signed a treaty with Sultan Mehmed IV recognizing the Cossack Hetmanate as a vassal of the Ottoman Empire?
...that the <a class="mw-redirect" href="./Cossack" id="mwBg8" rel="mw:WikiLink" title="Cossack">Cossack</a> <a href="./Hetman" id="mwBhA" rel="mw:WikiLink" title="Hetman">Hetman</a> and the later <a class="mw-disambig" href="./Muscovy" id="mwBhE" rel="mw:WikiLink" title="Muscovy">Muscovite</a> <a class="mw-redirect mw-disambig" href="./Voivod" id="mwBhI" rel="mw:WikiLink" title="Voivod">voyevoda</a> <b id="mwBhM"><a href="./Petro_Doroshenko" id="mwBhQ" rel="mw:WikiLink" title="Petro Doroshenko">Petro Doroshenko</a></b> signed a treaty with <a href="./Sultan" id="mwBhU" rel="mw:WikiLink" title="Sultan">Sultan</a> <a href="./Mehmed_IV" id="mwBhY" rel="mw:WikiLink" title="Mehmed IV">Mehmed IV</a> recognizing the <a href="./Cossack_Hetmanate" id="mwBhc" rel="mw:WikiLink" title="Cossack Hetmanate">Cossack Hetmanate</a> as a <a href="./Vassal" id="mwBhg" rel="mw:WikiLink" title="Vassal">vassal</a> of the <a href="./Ottoman_Empire" id="mwBhk" rel="mw:WikiLink" title="Ottoman Empire">Ottoman Empire</a>?