具有反馈控制和收获项的时滞单物种模型两个周期解的存在性
田德生, 蔡光兴, 杨策平
Existence of Two Periodic Solutions of a Delayed Single Species Model with Feedback Regulation and Harvest Term 
TIAN De-sheng, CAI Guang-xing, YANG Ce-ping
数学季刊 . 2010, (3): 407 -413 .