The tremendous increase in patenting among academics raises the logical question of the degree to which patents affect the sharing of material. Recent work by John Walsh, Charlene Cho, and Wes Cohen examines how patenting affects access to material and finds that it is largely unaffected, primarily because of issues related to lack of enforceability. Only 1 percent of academic researchers reported that they had delayed a project due to the patents of others; none reported abandoning a project. Moreover, only 5 percent reported that they regularly checked to see if their research could be affected by relevant patents, suggesting that infringement is of little concern. But not all institutions wink and look the other way when infringement occurs. Several cases of strong patent enforcement have been widely documented that have affected research. A recent example concerns human embryonic stem cells. The University of Wisconsin, whose researchers discovered them, has used its control, both through patents and material rights to the cell lines, to impose limits and conditions on use by other academics.