@article{IM_1970__11_142062,
     author = {Ch.H. Giffen},
     title = {Diffeotopically {Trivial} {Periodic} {Diffeomorphisms.}},
     journal = {Inventiones mathematicae},
     pages = {340--348},
     publisher = {mathdoc},
     volume = {11},
     year = {1970},
     zbl = {0214.22902},
     url = {http://geodesic.mathdoc.fr/item/IM_1970__11_142062/}
}