Shibly, Hassan, and Orwah H. Shibly. “Formulation Method of Gain Calculation at Marginal Stability of a Linear Invariant Control Systems”. Applications of Modelling and Simulation, vol. 7, Mar. 2023, pp. 16-28, https://www.ojs.arqiipubl.com/index.php/AMS_Journal/article/view/382.