@article{10_4171_ifb_311,
     author = {John Andersson and Erik Lindgren and Henrik Shahgholian},
     title = {Optimal regularity for the parabolic no-sign obstacle type problem},
     journal = {Interfaces and free boundaries},
     pages = {477--499},
     year = {2013},
     volume = {15},
     number = {4},
     doi = {10.4171/ifb/311},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ifb/311/}
}