A blueprint for the formalization of Seymour's matroid decomposition theorem
I. Sergeev, M. Dvorak, C. Rampell, M. Sandey, P. Monticone, ArXiv (n.d.).

Composition direction of Seymour's theorem for regular matroids — Formally verified
M. Dvorak, T. Figueroa-Reid, R. Hamadani, B.-H. Hwang, E. Karunus, V. Kolmogorov, A. Meiburg, A. Nelson, P. Nelson, M. Sandey, I. Sergeev, ArXiv (n.d.).