| [1] | 
D.V. Alekseevsky, C. Medori, A. Tomassini: "Homogeneous para-Kähler Einstein manifolds",  arXiv:math.DG/0806.2272  | 
| [2] |  
D.V. Alekseevsky, C. Medori, A. Tomassini: "Maximally homogeneous para-CR manifolds  of semisimple type", arXiv:math.DG/0808.0431  |