four double centuries
... that Michael Clarke is the only player to score four double centuries during a calendar year, and the third to achieve two double centuries in a series twice?
... that <a href="./Michael_Clarke_(cricketer)" id="mwrg" rel="mw:WikiLink" title="Michael Clarke (cricketer)">Michael Clarke</a> is the only player to score <b id="mwrw"><a href="./List_of_international_cricket_centuries_by_Michael_Clarke" id="mwsA" rel="mw:WikiLink" title="List of international cricket centuries by Michael Clarke">four double centuries</a></b> during a calendar year, and the third to achieve two double centuries in a series twice?