Select DISTINCT(yr) from (select year(issue_date) as yr, issue_date from paper_master,printsize_master,stamps where issue_date!='' and  paper_master.paper_code=stamps.paper_code and paper_master.paper='Watermarked Adhesive stamp paper with 'Ashoka Pillar''  and stamps.serial_no='0668'  and printsize_master.printsize_code=stamps.printsize_code and printsize_master.printsize='3.56 x 2.5'  order by issue_date) t