[B] Boeckx E.: Einstein-like semi-symmetric spaces. Arch. Math. (Brno) 29 (1993), 235–240. MR 1263125 | Zbl 0807.53041

[BC] Boeckx E., Calvaruso G.: When is the unit tangent sphere bundle semi-symmetric?. preprint 2002. MR 2075771 | Zbl 1076.53032

[BKV] Boeckx E., Kowalski O., and Vanhecke L.: Riemannian manifolds of conullity two. World Scientific 1996. MR 1462887

[CV] Calvaruso G., Vanhecke L.: Semi-symmetric ball-homogeneous spaces and a volume conjecture. Bull. Austral. Math. Soc. 57 (1998), 109–115. MR 1623824 | Zbl 0903.53031

[HSk] Hashimoto N., Sekizawa M.: Three-dimensional conformally flat pseudo-symmetric spaces of constant type. Arch. Math. (Brno) 36 (2000), 279–286. MR 1811172 | Zbl 1054.53060

[K] Kurita M.: On the holonomy group of the conformally flat Riemannian manifold. Nagoya Math. J. 9 (1975), 161–171. MR 0074050

[R] Ryan P.: A note on conformally flat spaces with constant scalar curvature. Proc. 13th Biennal Seminar of the Canadian Math. Congress Differ. Geom. Appl., Dalhousie Univ. Halifax 1971, 2 (1972), 115–124. MR 0487882

[S] Szabó Y. I.: Structure theorems on Riemannian manifolds satisfying $R(X,Y) \cdot R=0$. I, the local version, J. Differential Geom. 17 (1982), 531–582. MR 0683165

[T] Takagi H.: An example of Riemannian manifold satisfying $R(X,Y) \cdot R$ but not $\nabla R =0$. Tôhoku Math. J. 24 (1972), 105–108. MR 0319109