Chen, A., and J. L. Shen. “A Note on Property (gaR) and Perturbations”. Ukrains’kyi Matematychnyi Zhurnal 69, no. 7 (July 25, 2017): 974-983. Accessed October 3, 2022. http://umj.imath.kiev.ua/index.php/umj/article/view/1750.