1. [1] V. Andrejić, “On certain classes of algebraic curvature tensors” in Proceedings of the 5th Summer School in Modern Mathematical Physics (Belgrade, 2008), Inst. Phys., Belgrade, 2009, 43–50.
2. [2] V. Andrejić, Strong duality principle for four-dimensional Osserman manifolds, Kragujevac J. Math. 33 (2010), 17–28.
3. [3] V. Andrejić, Duality principle for Osserman manifolds (in Serbian), Ph.D. dissertation, Belgrade, 2010.
4. [4] V. Andrejić and Z. Rakić, On the duality principle in pseudo-Riemannian Osserman manifolds, J. Geom. Phys. 57 (2007), 2158–2166.
5. [5] N. Blažić, N. Bokan, and P. Gilkey, A note on Osserman Lorentzian manifolds, Bull. Lond. Math. Soc. 29 (1997), 227–230.