@Other{ApushkinskayaMatevosyanUraltseva_2006,
title={Regularity of a free boundary in parabolic problem without sign restriction},
author={Apushkinskaya, Darya and Matevosyan, Norayr and Uraltseva, Nina},
doi={http://dx.doi.org/10.22028/D291-26351},
year={2006}
}