J. J. Mohan, R. K. Jha, G. Pradeep Kumar, A. M. Dharmarajan, and M. Laloraya, “Secreted Frizzle-Related Protein (sFRP4) can Abrogate Pregnancy - A New Dimension in its Biological Role”, JER, vol. 11, no. 1, pp. 41–44, Jun. 2007.