1. Ordering by divisibility in abstract algebras;Higman;Proc. Lond. Math. Soc.,1952
2. On ordered division rings;Neumann;Trans. Amer. Math. Soc.,1949
3. Partial well-ordering of sets of vectors;Rado;Mathematika,1954
4. The theory of well-partially-ordered sets;Kruskal,1954
5. Well-quasi-ordering, the tree theorem, and Vazsonyi's conjecture;Kruskal;Trans. Amer. Math. Soc.,1960