ABSTRACT
Lisette Ibanez* and Jacques Laye UMR ENGREF-INRA LEF, 14 rue Girardot, Nancy Cedex, 54042 France Fax: +33-3-83-37-06-45 E-mail: ibanez@nancy-engref.inra.fr E-mail: laye@ nancy-engref.inra.fr Corresponding author
1 Introduction
2 The model
3 Results
4 Concluding remarks
References
Appendix
n — e s -^e+^s-4 k&-ks
Notes
