@article{ASNSP_2004_5_3_2_349_0,
     author = {Guti\'errez, Cristian E. and Montanari, Annamaria},
     title = {On the second order derivatives of convex functions on the {Heisenberg} group},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {349--366},
     publisher = {Scuola Normale Superiore, Pisa},
     volume = {Ser. 5, 3},
     number = {2},
     year = {2004},
     mrnumber = {2075987},
     zbl = {1170.35352},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_2004_5_3_2_349_0/}
}