摘要：This article presents the first formalization of Kurskal's tree theorem in a proof assistant. The Isabelle/HOL development is along the lines of Nash-Williams' original minimal bad sequence argument for proving the tree theorem. Along the way, proofs of Dickson's lemma and Higman's lemma, as well as some technical details of the formalization are discussed.
关键词：almost-full relations;well-quasi-orders;Dickson's lemma;HIgman's lemma;Kruskal's tree theorem;minimal bad sequences
