“…In the past years, the research work upon delay differential equations becomes more and more popular [3,[5][6][7][11][12][13]15,[17][18][19], because this kind of differential equations also have broad applied backgrounds in the fields of physics, biology and control principle [1,4]. The relative differential equations include two kinds, ie, differential equations with eigenvalues (see [3,7,14,18]) or without eigenvalues [13,13,15].…”