Pappus's theorem and the modular group Richard Evan Schwartz (1993) Publications Mathématiques de l'IHÉS
Projective collineations as products of homologies, elations, and projective reflections. (Short Communication). Erich W. Ellers (1982) Aequationes mathematicae
Projective collineations as products of homologies, elations, and projective reflections. Erich W. Ellers (1982) Aequationes mathematicae