1. Graph Theory;Diestel,2010
2. Theory of Relations, Studies in Logic and the Foundations of Mathematics;Fraïssé,2000
3. Ordering by divisibility in abstract algebras;Higman;Proc. Lond. Math. Soc.,1952
4. Well-quasi-ordering, the tree theorem, and Vazsonyi's conjecture;Kruskal;Trans. Am. Math. Soc.,1960
5. On well-quasi-ordering lower sets of finite trees;Nash-Williams;Proc. Camb. Philol. Soc.,1964