International Mathematical Forum. Journal for Theory and Applications (Int. Math. Forum) (20130101), 8, no.~5-8, 237-243. ISSN: 1312-7594 (print).eISSN: 1314-7536.
International Mathematical Forum. Journal for Theory and Applications (Int. Math. Forum) (20120101), 7, no.~53-56, 2759-2766. ISSN: 1312-7594 (print).eISSN: 1314-7536.