1. E. Abbena, S. Garbiero and L. Vanhecke,Einstein-like metrics on three-dimensional Riemannian homogeneous manifolds, Simon Stevin66 (1992), 173–182.
2. Proc. Conf. Opava/Czechoslovakia;J. Berndt,1993
3. Lecture Notes in Mathematics;D. E. Blair,1976
4. D. E. Blair,On the existence of conformally flat contact metric 3-manifolds, preprint, 1996.
5. D. E. Blair, T. Koufogiorgos and B.J. Papantoniou,Contact metric manifolds satisfying a nullity condition, Israel Journal of Mathematics91 (1995), 189–214.