@article{ASNSP_1971_3_25_1_41_0,
     author = {Allegretto, W.},
     title = {A comparison theorem for nonlinear operators},
     journal = {Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche},
     pages = {41--46},
     publisher = {Scuola normale superiore},
     volume = {Ser. 3, 25},
     number = {1},
     year = {1971},
     mrnumber = {298181},
     zbl = {0225.35013},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1971_3_25_1_41_0/}
}