Chunling, Tong, Xiaohui, Lin, Yuansheng, Yang, Feng, Xue, and Huapingc, Jiang. “A Note on the Cyclic Connectivity Property of Directed Graphs”. Utilitas Mathematica, vol. 85, June 2011, https://utilitasmathematica.com/index.php/Index/article/view/775.