摘要：We study the existence of positive periodic solutions of the second-order difference equation Δ 2 u ( t - 1 ) + a ( t ) u ( t ) = f ( t , u ( t ) ) + c ( t ) , t ∈ ℤ via Schauder's fixed point theorem, where a, c : ℤ → ℝ+ are T -periodic functions, f ∈ C(ℤ × (0, ∞), ℝ) is T -periodic with respect to t and singular at u = 0. Mathematics Subject Classifications: 34B15.
