@article{PMIHES_1993__77__5_0,
     author = {Grayson, Matthew and Pugh, Charles},
     title = {Critical sets in 3-space},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {5--61},
     publisher = {Institut des Hautes \'Etudes Scientifiques},
     volume = {77},
     year = {1993},
     mrnumber = {94k:57049},
     zbl = {0796.58012},
     language = {en},
     url = {http://www.numdam.org/item/PMIHES_1993__77__5_0/}
}