@article{LetchfordPokuttaSchulz2011, author = {A.N. Letchford and Sebastian Pokutta and A.S. Schulz}, title = {On the membership problem for the 0,1/2-closure}, journal = {Operations Research Letters}, volume = {39}, number = {5}, pages = {301 -- 304}, url = {http://www.box.net/shared/zxx88q38l3}, year = {2011}, }