Lightlike ruled surfaces in ℝ 1 4 . Kılıç, Erol; Karadaǧ, H.Bayram — 2006 Balkan Journal of Geometry and its Applications (BJGA)
Invariant submanifolds of Sasakian manifolds. Karadağ, H.Bayram; Atçeken, Mehmet — 2007 Balkan Journal of Geometry and its Applications (BJGA)