Let U,V⊂RnU,V\subset\mathbb R^nU,V⊂Rn be open. A class CkC^kCk diffeomorphism is a bijective CkC^kCk function g:U→Vg:U\to Vg:U→V such that the inverse g−1g^{-1}g−1 is also of class CkC^kCk.
Wikidata ID: Q1058314