1. Some Unitals on 28 Points and Their Embeddings in Projective Planes of Order Nine;Brouwer;Math. Centrum, ZW 155/81,1981
2. Subplanes of the Hughes plane of order 9;Denniston,1965
3. On k-sets of type (m, n) in projective planes of square order;de Finis,1981
4. On k-sets in a Steiner system S(2, l, v);de Resmini,1981
5. Aninfinite family of type (m, n) sets in PG(2, q2), q a square;de Resmini;J. Geom.,1983