@article{JRAM_1989__401_153176,
     author = {Klaus Steffen and Frank Duzaar},
     title = {An optimal estimate for the singular set of a harmonic map in the free boundary.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {157--187},
     publisher = {mathdoc},
     volume = {401},
     year = {1989},
     zbl = {0679.35015},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1989__401_153176/}
}