Osteoprotegerin: a novel secreted protein involved in the regulation of bone density. - Simonet,W.S.; Lacey,D.L.; Dunstan,C.R.; Kelley,M.; Chang,M.S.; Luthy,R.; Nguyen,H.Q.; Wooden,S.; Bennet,L.; Boone,T.; Shimamoto,G.; DeRose,M.; et al. (Cell, 1997)