Convent, A., and J. Van Schaftingen. “Intrinsic Colocal Weak Derivatives and Sobolev Spaces Between manifolds ”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE, vol. 16, no. 1, Mar. 2016, pp. 97-128, doi:10.2422/2036-2145.201312_005.