Hello Ines: You can look this one also, incase you can not get hold of the references given to you already by Mr Kakani. Ritchie, J.T. 1985. A user oriented model of soil water balance in wheat. p.293-305. In: W.Day and R.K. Atkins. (ed.) Wheat growth and modelling.Plenum Press, NY. Alagarswamy _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com.