中国科学院数学与系统科学研究院期刊网
Variation of Parameters Formula and Gronwall Inequality for Differential Equations with a General Piecewise Constant Argument
Kuo-Shou CHIU, Manuel PINTO
Acta Mathematicae Applicatae Sinica(English Series) . 2011, (4): 561 -568 .  DOI: 10.1007/s10255-011-0107-5