Francesconi, G, Orera, A., Headspith, D., Francesconi, M. G., Apperley, D. C., Francesconi, M. Grazia, Slater, P. R., "Formation of apatite oxynitrides by the reaction between apatite-type oxide ion conductors, La8+xSr2-x(Si/Ge)6O26+x/2, and ammonia", Journal of Solid State Chemistry, 2009