Aloyce, Melkiory M., Santosh Kumar, and Marco Mpimbo. 2021. “On Scalar Multiples of Hypercyclic Operators on Non-Normable and Separable Fréchet Spaces”. Tanzania Journal of Science 45 (3):431-38. https://tjs.udsm.ac.tz/index.php/tjs/article/view/211.