Some properties of controlled K-frames in Hilbert spaces

In this paper, we reintroduce the concept of controlled K-frames and then, we show that this definition is equivalentwith the concept that has been recently introduced in \cite{Nouri}. Meanwhile, we correctone of the results which was obtained in the mentioned paper. In the sequel, we construct some new controlled K-framesby some operator theory tools. Finally, we provide some conditions under which the sum of two controlled K-frames remainsa controlled K-frame.