@article{JRAM_1992__430_153446,
     author = {A.G. O'Farrell and R.O. Watson},
     title = {The tangent stars of a set, and extensions of smooth functions.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {109--138},
     publisher = {mathdoc},
     volume = {430},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1992__430_153446/}
}