Distinct on a group by

Hello,
I have the below query:

SELECT distinct
       V.date_create as CREATEDDATE,        
       LTRIM(RTRIM(V.VENDOR_CODE)) as VENDORCODE,     
       V.VENDOR_NAME as VENDOR_NAME,
min(po_num),ph.date_create,ww_buyer
		       
  FROM d_vendors V 
inner join m_pohead ph  on  V.VENDOR_CODE = ph.vendor_code

WHERE
V.date_create >= '11-01-2014'
group by v.date_create,v.vendor_code,v.vendor_name,ph.date_create,ww_buyer
order by vendorcode

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Please let me know how to modify this query so that for a vendor code it returns only the least po_num ,currently its returning multiple Po's because of the grouping on each row.Po num are unique values in the m_pohead table