San Francisco 49ers head coaches
... that Jack Christiansen and Bill Walsh are the only San Francisco 49ers head coaches in the Pro Football Hall of Fame?
... that <a href="./Jack_Christiansen" id="mwAmE" rel="mw:WikiLink" title="Jack Christiansen">Jack Christiansen</a> and <a href="./Bill_Walsh_(American_football_coach)" id="mwAmI" rel="mw:WikiLink" title="Bill Walsh (American football coach)">Bill Walsh</a> are the only <b id="mwAmM"><a href="./List_of_San_Francisco_49ers_head_coaches" id="mwAmQ" rel="mw:WikiLink" title="List of San Francisco 49ers head coaches">San Francisco 49ers head coaches</a></b> in the <a href="./Pro_Football_Hall_of_Fame" id="mwAmU" rel="mw:WikiLink" title="Pro Football Hall of Fame">Pro Football Hall of Fame</a>?