1. Axiomatic treatment of rank in infinite sets;Rado;Can. J. of Math.,1949
2. A colour problem for infinite graphs and a problem in the theory of relations;de Bruijn,1951
3. Choice functions and Tychonoff's theorem;Gottschalk,1951
4. Short proof of a theorem of Rado on graphs;Foster,1964
5. A remark on a paper by N. G. de Bruijn and P. Erdös;Luxemburg,1962