@article{CMH_1974__49_139598,
     author = {John N. Mather},
     title = {Commutators of {Diffeomorphisms}},
     journal = {Commentarii mathematici Helvetici},
     pages = {512--528},
     publisher = {mathdoc},
     volume = {49},
     year = {1974},
     zbl = {0289.57014},
     url = {http://geodesic.mathdoc.fr/item/CMH_1974__49_139598/}
}