@article{ASNSP_1973_3_27_1_97_0,
     author = {Bruckner, A. M. and Thorne, Charles L.},
     title = {Density covers},
     journal = {Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche},
     pages = {97--104},
     publisher = {Scuola normale superiore},
     volume = {Ser. 3, 27},
     number = {1},
     year = {1973},
     mrnumber = {417393},
     zbl = {0256.26004},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1973_3_27_1_97_0/}
}