On restrictions of automorphism groups of compact projective planes to subplanes
The authors show that the restriction of a compact projective plane to a closed Baer subplane, or to an open subgeometry, is a quotient mapping. This contrasts with restrictions to arbitrary subgeometries. In the proof, they investigate lineations in towers of Baer subplanes. No connectedness assumptions are needed. The notions and the necessity of the assumptions are illustrated by examples.
scientific article; zbMATH DE number 62172