1. CASAS, E. and XAMBO, S.: "Enumerative theory of conics in IPn", X Jornadas Hispano-lusas de Matemáticas, Murcia, 1985.
2. CORAY, D. and VAINSENCHER, I.: "Enumerative formulae for ruled surfaces and rational quintic curves", Comment. Math. Helvetici 61 (1986) 501–518.
3. FULTON, W.: Intersection Theory, Ergebnisse der mathematik und ihrer Grenzgebiete 3. Folge, Band 2. Springer-Verlag, 1984.
4. FULTON, W., KLEIMAN, S. and MACPHERSON, R.: "About the enumeration of contacts", Algebraic Geometry-Open Problems, Proceedings, Ravello 1982, ed. C. Ciliberto, F. Ghione and F. Orecchia, Springer Lecture Notes, no. 997 (1983), 156–196.
5. GOLDSTEIN, N.: "The Geometry of Surfaces in the 4-Quadric", Preprint, Univ. British Columbia, 1984.