HAIDER, S. M. K., KHAN , . V. A. and HUSAIN, S. I. (1993) “TOTALLY UMBILICAL SEMI-INVARIANT SUBMANIFOLDS AND CR-SUBMANIFOLDS OF A SASAKIAN MANIFOLD”, Tamkang Journal of Mathematics, 24(2), pp. 161–172. doi: 10.5556/j.tkjm.24.1993.4486.