@article{PMIHES_1967__33__21_0,
     author = {John. M. Boardman},
     title = {Singularities of differentiable maps},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {21--57},
     year = {1967},
     publisher = {Institut des Hautes \'Etudes Scientifiques},
     volume = {33},
     doi = {10.1007/BF02684585},
     mrnumber = {231390},
     zbl = {0165.56803},
     language = {en},
     url = {https://pmihes.centre-mersenne.org/articles/10.1007/BF02684585/}
}