Walpole, P. <br/><br/>
Food production systems:  crops and their environment, unit 3 

 - Milton Keynes  The Open University Press  1978 
 - 48p.  illus. 
<br/><br/><label>ISBN: </label>0335063713 
<br/><br/><label>LC Class. No.: </label>S600  / .F68 1978