Poincaré duality
...that Henri Poincaré first stated the Poincaré duality in terms of Betti numbers?
...that <a href="./Henri_Poincaré" id="mwAdY" rel="mw:WikiLink" title="Henri Poincaré">Henri Poincaré</a> first stated the <b id="mwAdc"><a href="./Poincaré_duality" id="mwAdg" rel="mw:WikiLink" title="Poincaré duality">Poincaré duality</a></b> in terms of <a class="mw-redirect" href="./Betti_numbers" id="mwAdk" rel="mw:WikiLink" title="Betti numbers">Betti numbers</a>?