Nonplanar on-shell diagrams and leading singularities of scattering amplitudesBaoyi Chen, Gang Chen, Yeuk-Kwan E. Cheung, Yunxuan Li, Ruofei Xie and Yuan XinEur. Phys. J. C, 77 2 (2017) 80DOI: https://doi.org/10.1140/epjc/s10052-017-4659-2