“…There is plenty of evidence suggesting that when delays happen, problems can develop, causing degradation to the system’s performance and potentially leading the system to an unstable state. Therefore, stability problems have been highlighted in the literature not only for positive systems (Gurvits et al, 2007; Silva–Navarro and Alvarez–Gallegos, 1997; Zhao et al, 2014, 2012), but also for delay systems (Elloumi et al, 2016; Kwon and Park, 2004; Kwon et al, 2014; Liu et al, 2010; Shen and Wang, 2015; Sun et al, 2007; Wang et al, 2015, 2013; Xiang et al, 2012a,b, 2013; Zhu et al, 2012). In Zhu et al (2012), the exponential stability problems of the continuous-time and discrete-time positive systems with constant delay have been addressed by using the Lyapunov–Krasovskii functional method and the asymptotical stability results of positive linear delay systems.…”