“…See, for example, Sunkel, Shieh, and Zhang (1991), Shieh, Wang, and Zheng (1997), Chang, Park, Lee, and Joo (2002), Lee, Park, and Joo (2003), Tsai, Tsai, and Guo (2007), respectively, and references therein. By comparison, relatively few related results seem to be tractable for nonlinear systems (Guo, Shieh, Chen, and Lin 2000;Chang, Park, and Joo 2003;Nesˇic´and Gru¨ne 2005Gru¨ne, Worthmann, and Nesˇic´2008;Lee, Shieh, and Kim 2008).…”