@article{Ahangar_2018, title={Stability and Asymptotic Behavior of the Causal Operator Dynamical Systems Using Nonlinear Variation of Parameters}, volume={13}, url={http://www.scitecresearch.com/journals/index.php/jprm/article/view/1364}, number={1}, journal={Journal of Progressive Research in Mathematics}, author={Ahangar, Reza}, year={2018}, month={Jan.}, pages={2170-2189}