R. Lashkaripour,D. Foroutannia, Dept. of Math., Sistan and Baluchestan University, Zahedan, Iran, e-mail:lashkari@hamoon.usb.ac.ir,d_foroutan@math.com

**Abstract:** In this paper we consider the problem of finding upper bounds of certain matrix operators such as Hausdorff, Norlund matrix, weighted mean and summability on sequence spaces $l_p(w)$ and Lorentz sequence spaces $d(w,p)$, which was recently considered in [9] and [10] and similarly to [14] by Josip Pecaric, Ivan Peric and Rajko Roki. Also, this study is an extension of some works by G. Bennett on $l_p$ spaces, see [1] and [2].

**Keywords:** inequality, norm, summability matrix, Hausdorff matrix, Norlund matrix, weighted mean matrix, weighted sequence space and Lorentz sequence space

**Classification (MSC 2000):** 47-99, 15A60

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