1. Andreotti, A., Nacinovich, M.: Complexes of Partial Differential Operators. Ann. Sc. Normale Superiore-Pisa Sc. S.IV?III, 553?621 (1976)
2. Babbage, D.W.: Multiple canonical surfaces Proc. Cambridge Phil. Soc. Vol. XXX (1934)
3. Barth, W.: Counting singularities of quadratic forms on vector bundles. Preprint
4. Beauville, A.: L'application canonique pour les surfaces de type general, Inv. Math.55, 121?140 (1979)
5. Beauville, A.: Sur le nombre maximum de point doubles d'une surface dans? 3(µ(5)=31) Proceedings of the Angers Conference 1979