@article{ASNSP_1979_4_6_1_151_0,
     author = {Caffarelli, Luis A. and Friedman, Avner},
     title = {The obstacle problem for the biharmonic operator},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {151--184},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 6},
     number = {1},
     year = {1979},
     mrnumber = {529478},
     zbl = {0405.31007},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1979_4_6_1_151_0/}
}