He Z, Zhu H, Ding L, Xiao H, Chen D, Xue F. Association of NPP1 polymorphism with postoperative progression of ossification of the posterior longitudinal ligament in Chinese patients. Genet Mol Res. 2013 Oct 18;12(4):4648–55. doi: 10.4238/2013.october.18.3. PMID: 24222241.