“…On the other hand, the topics of absolute stability and hyperstability are of a very relevant interest even nowadays because of their theoretical importance and its wide range of applications including stabilization under parametrical dispersion of regulator components either in the absence or in the presence of delays, hybrid mixed continuous-time and digital systems or passivity issues. See, for instance, some recent related background in Braverman & Zhukovskly (2012), Chen et al (2011), Duarte-Mermoud et al (2012), Song & Cao (2008), Tai (2012), Tai & Lun (2012), Zhou et al (2009) and references therein. Also, the property of absolute stability has been also investigated for systems involving timedelays; see, for instance, Wu et al (2009) and references therein.…”