1. [AS] Andreatta, M., Sommese, A.J.: On the adjunction mapping for singular projective varieties. Forum Math.1, 143?152 (1989)
2. [ArS] Arrondo, E., Sols, I.: Classification of smooth congruences of low degree. J. Reine Angew. Math.393, 199?219 (1989)
3. [B1] B�descu, L.: On ample divisors. Nagoya Math. J.86, 155?171 (1982)
4. Teubner-Texte Math.;L. B�descu,1981
5. [B3] B�descu, L.: The projective plane blow-up at a point as an ample divisor. Rend. Accad. Ligure Sci. Lett.38, 3?7 (1981)