Hong Yao, John A Robertson, Eun-Ah Kim, Steven A KivelsonPhys. Rev. B 74, 245126. DOI: http://dx.doi.org/10.1103/PhysRevB.74.245126. arXiv:cond-mat/0606304. Thursday, December 28, 2006 Phys. Rev. B 2006 Yao-1.pdf