@article{ASNSP_1990_4_17_1_1_0,
     author = {Ruf, Bernhard},
     title = {Singularity theory and the geometry of a nonlinear elliptic equation},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {1--33},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 17},
     number = {1},
     year = {1990},
     mrnumber = {1074625},
     zbl = {0725.35043},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1990_4_17_1_1_0/}
}