* {{cite book | last=Cartan | first=Elie | title=On Manifolds with an Affine Connection and the Theory of General Relativity | publisher=Bibliopolis | publication-place=Napoli | date=1986 | isbn=88-7088-086-9}}
<ref name="g847">{{cite book | last=Cartan | first=Elie | title=On Manifolds with an Affine Connection and the Theory of General Relativity | publisher=Bibliopolis | publication-place=Napoli | date=1986 | isbn=88-7088-086-9 | page=}}</ref>