@article{JRAM_1984__355_152687,
     author = {Horst Kn\"orrer},
     title = {Singular fibres of the momentum mapping for integrable {Hamiltonian} systems.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {67--107},
     publisher = {mathdoc},
     volume = {355},
     year = {1984},
     zbl = {0542.58005},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1984__355_152687/}
}