@article{IM_1985__82_143292,
     author = {J., Takens, F. Palis},
     title = {Cycles and measure of bifurcation sets for two-dimensional diffeomorphisms.},
     journal = {Inventiones mathematicae},
     pages = {397--422},
     year = {1985},
     volume = {82},
     zbl = {0579.58005},
     url = {http://geodesic.mathdoc.fr/item/IM_1985__82_143292/}
}