Using case in formula fields of sfdc

CASE(MONTH(Mon_Field__c ), 01, 'January/2012', 02, 'February/2012',03, 'March/2012',04,'April/2012',05, 'May/2012',06,'June/2012',07,'July/2012',08,'August/2012',09, 'September/2012',10,'October/2012',11,'November/2012',12,'December/2012','')

* In the above formula, to display year dynameically intead of 'January/2012' use like below:
'January/'+Text( YEAR(Mon_Field__c ))