Ekmekci, F. N., and G. Tuğ. “Notes on the Lightlike Hypersurfaces Along Spacelike Submanifolds”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 71, no. 7, July 2019, pp. 968-75, http://umj.imath.kiev.ua/index.php/umj/article/view/1490.