On combinatorial characterization of planar $st$ graphs. - Sen Hu; Xuexing Lu; Yu Ye (CoRR, 2016)

Combinatorial characterization of upward planarity. - Xuexing Lu; Yu Ye (CoRR, 2016)

A Graphical Calculus for Semi-Groupal Categories. - Xuexing Lu; Yu Ye; Sen Hu (Appl. Categorical Struct., 2019)

A composition theory for upward planar orders. - Xue Dong; Xuexing Lu; Yu Ye (CoRR, 2025)