Chaos threshold analysis of Duffing oscillator with fractional-order delayed feedback controlShaofang Wen, Hao Qin, Yongjun Shen and Jiangchuan NiuEur. Phys. J. Spec. Top., 231 11-12 (2022) 2183-2197DOI: https://doi.org/10.1140/epjs/s11734-021-00369-6