sql query is giving repeatative data

select a.invoice_no, 
       a.item_no ,
       b.item ,
       (a.invoice_qty * b.per_qty),
       c.std_purchase_price 
from shp..dms_t_invoice_item a
left outer join pmddb..bom_stock_tb b 
on b.fg = a.item_no 
left outer join pomdb..pur_vendor_stock c
on c.stock_no = b.item  
where a.acsd_date between '2014-04-01 00:00:00.000' and '2014-04-30 00:00:00.000'
order by a.invoice_no