Two existence theorems of periodic solutions for differential delay equations
An error in the paper [\textit{K. Wang}, Chin. Ann. Math. Ser. B 11, No. 4, 438-444 (1990; Zbl 0729.34047)] is pointed out. Under new assumptions, existence of periodic solutions is proved for the equation \(x'(t) = f(x(t), x(t-1))\).
scientific article; zbMATH DE number 640441