Let A be a reduced incidence relation between n lines and m points. Suppose that Through each two points there pass lines Each two lines intersect in points. If assume, moreover, that there are four points no three of which are on one line. Then , , and there is a number r such that all lines have r points and through each point there pass r lines. The number r is given by .

, , , , ,
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Department of Analysis, Algebra and Geometry [AM]

Hazewinkel, M. (1995). Linked balanced designs are symmetric BIBD's. Department of Analysis, Algebra and Geometry [AM]. CWI.