Variationally asymptotically stable difference systems. Choi, Sung Kyu; Goo, Yoon Hoe; Koo, Namjip — 2007 Advances in Difference Equations [electronic only]
h -stability of dynamic equations on time scales with nonregressivity. Choi, Sung Kyu; Goo, Yoon Hoe; Koo, Namjip — 2008 Abstract and Applied Analysis
Total stability in nonlinear discrete Volterra equations with unbounded delay. Choi, Sung Kyu; Goo, Yoon Hoe; Im, Dong Man; Koo, Namjip — 2009 Abstract and Applied Analysis