* {{cite book | last=Quine | first=Willard Van Orman | title=Theories and Things | publisher=Harvard University Press | publication-place=Cambridge, Mass. | date=1981 | isbn=0-674-87926-0}}
<ref name="r648">{{cite book | last=Quine | first=Willard Van Orman | title=Theories and Things | publisher=Harvard University Press | publication-place=Cambridge, Mass. | date=1981 | isbn=0-674-87926-0 | page=}}</ref>