1. R. Baer, Partitionen endicher Gruppen, Math. Zeit., 75 (1961), 333–372.
2. D. Gorenstein, Finite Groups, Harper and Row, N. Y., 1968.
3. H. Karzel and G. Kist, Finite porous incidence groups and S-homogeneous 2-sets. 1st. Naz. di Alta Matematica, to appear.
4. H. Karzel and C. J. Maxson, Kinematic spaces with dilatations, J. of Geometry, to appear.
5. H. Karzel, K. SÖrenson and D. Windelberg, Einführung in die Geometrie, Vandenhoeck und Ruprecht, Göttingen, 1973.