Damak, H., M. A. Hammami, and A. Kicha. “A Converse Theorem for Practical $h$-Stability of Time-Varying Nonlinear Systems”. New Zealand Journal of Mathematics 50 (February 4, 2021): 109–123. Accessed November 27, 2024. https://nzjmath.org/index.php/NZJMATH/article/view/79.