@misc{ZouVeeserKornhuberetal.2009, author = {Qingsong Zou and Andreas Veeser and Ralf Kornhuber and Carsten Gr{\"a}ser}, title = {Hierarchical error estimates for the energy functional in obstacle problems}, institution = {Freie Universit{\"a}t Berlin}, type = {preprintmatheon}, year = {2009}, }