@article{ASNSP_1994_4_21_2_157_0,
     author = {Sakaguchi, Shigeru},
     title = {Critical points of solutions to the obstacle problem in the plane},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {157--173},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 21},
     number = {2},
     year = {1994},
     mrnumber = {1288362},
     zbl = {0823.35068},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1994_4_21_2_157_0/}
}