1. Cartan, E. Systèmes Différentiels Extérieurs et Leurs Applications Géométriques. Hermann, Paris, 1975.
2. Dieudonné, J. Elements d’Analyse, Vol. IV. Gauthier Villars, Paris, 1977.
3. Matsumoto, K., Mihai, A., and Rosca, R. Riemannian manifolds carrying a pair of skew symmetric Killing vector field. An. Şt. Univ. “Al. I. Cuza” Iaşi, 2003, 49, 137–146.
4. Mihai, I., Rosca, R., and Verstraelen, L. Some Aspects of the Differential Geometry of Vector Fields. K.U. Leuven, K.U. Brussel, PADGE 2, 1996.
5. O’Neill, B. Semi-Riemannian Geometry. Academic Press, 1983.
6. Poor, W. A. Differential Geometric Structures. McGraw Hill, New York, 1981.
7. Reyes, E. and Rosca, R. On biconcircular gradient vector fields. Rend. Sem. Mat. Messina Serie II, 1999, 6 (21), 13–25.
8. Rosca, R. An exterior concurrent skew-symmetric Killing vector field. Rend. Sem. Mat. Messina, 1993, 2, 131–145.
9. Yano, K. On torse-forming directions in Riemannian spaces. Proc. Imp. Acad. Tokyo, 1984, 20, 340–345.
doi:10.3792/pia/1195572958