Configurations of Flats, I: Manifolds of Points in the Projective Line.

Jorge L. Arocha Javier Bracho Luis Montejano Configurations of Flats, I: Manifolds of Points in the Projective Line. 111-128 2005 34 Discrete & Computational Geometry 1 http://dx.doi.org/10.1007/s00454-005-1163-5 db/journals/dcg/dcg34.html#ArochaBM05