@article{ASNSP_1963_3_17_3_207_0,
     author = {Littman, Walter},
     title = {Generalized subharmonic functions : monotonic approximations and an improved maximum principle},
     journal = {Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche},
     pages = {207--222},
     publisher = {Scuola normale superiore},
     volume = {Ser. 3, 17},
     number = {3},
     year = {1963},
     mrnumber = {177186},
     zbl = {0123.29104},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1963_3_17_3_207_0/}
}