1. BETH,T., JUNGNICKEL,D. and LENZ,H.: Design Theory. Bibliographisches Institut, Mannheim 1985, and Cambridge University Press, Cambridge 1986
2. DRAKE, D.A. and JUNGNICKEL, D.: Klingenberg structures and partial designs I. Congruence relations and solutions. J. Stat. Planning Inf.1 (1977), 265?287.
3. DRAKE, D.A. and JUNGNICKEL, D.: Klingenberg structures and partial designs II. Regularity and uniformity. Pacific J. Math.77 (1978), 389?415.
4. DRAKE, D.A. and JUNGNICKEL, D.: Finite Hjelmslev planes and Klingenberg epimorphisms. NATO ASI Series C Vol.160 (1985), 153?231. Reidel, Dordrecht
5. JUNGNICKEL, D.: Some new combinatorial results on finite Klingenberg structures. Util. Math.16 (1979), 249?269.