Siemons, Johannes (1990) Automorphism groups as linear groups. In: Finite geometries and combinatorial designs (Lincoln, NE, 1987). Contemp. Math., 111 . American Mathematical Society, Providence, RI, pp. 309-312.
Siemons, Johannes and Böettcher, H. (1990) The concept of acceptability functions. In: Essays in Honor of Rolf Funck, Infrastructure and Space Economy. Springer, pp. 320-328.