1. Bremner J.M. 1965. Ann. Soc. of Agron., Madison, Wt, Agronomy, 9, 1149?1178.
2. Destain J., Guiot J., Francois E. and Riga. 1989. Plant and Soil 117, 117?183.
3. Destain J.P., Guiot J., Francois E. et Meeus-Verdinne K. 1991. Rev. Agriculture 441, 1, 89?100.
4. Guiot J., Goffart J.P. Destain J.P. 1992. Bull. Rech. Agron. 27, 1, 61?74.
5. Recous S., Machet J.M. and Mary B. 1992. Plant and Soil 144, 1, 101?111.