Retrieve month from date

I am using PGSQL 8.2.3 on Windows XP.<br /><br />I have a table called "StudentFeesPayment" with columns "ReceiptNo"
and"ReceiptMonthYear".<br />The column, "ReceiptMonthYear" stores date in the format "yyyy-mm-dd". I have to find the
max(ReceiptNo)where Month of (ReceiptMonthYear)=4. Or whatever month I give. <br /><br />I tried:<br /><br />Select
max(ReceiptNo)from StudentFeesPayment where Extract(Month('ReceiptMonthYear'))=4;<br /><br />But it is not working. How
todo it?<br /><br />