On the Existence of Periodic and Unbounded Solutions of Linear Differential Equations with Non-Negative Damping
L. E. Thomas · American Mathematical Monthly · 1972
L. E. Thomas, On the Existence of Periodic and Unbounded Solutions of Linear Differential Equations with Non-Negative Damping, The American Mathematical Monthly, Vol. 79, No. 10 (Dec., 1972), pp. 1107-1111