@article{JRAM_1989__393_153095,
     author = {Andrew Acker},
     title = {On the qualitative theory of parametrized families of free boundaries.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {134--167},
     publisher = {mathdoc},
     volume = {393},
     year = {1989},
     zbl = {0668.35090},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1989__393_153095/}
}