@article{ASNSP_1987_4_14_4_527_0,
     author = {Franchi, B. and Serapioni, R.},
     title = {Pointwise estimates for a class of strongly degenerate elliptic operators : a geometrical approach},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {527--568},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 14},
     number = {4},
     year = {1987},
     mrnumber = {963489},
     zbl = {0685.35046},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1987_4_14_4_527_0/}
}