On sharpness of sufficient conditions of stability for differential equations with delay

For stability of nonautonomous linear scalar equations with retarded argument and nonnegative coefficient, we consider conditions that have the form of an upper estimate for the integral of the coefficient over a certain interval. It is demonstrated that 2 is the least upper bound for the set of values of the integral that guarantee stability for some lenth of the interval of integration. The analogous result is obtained for a difference equation.