1. Quantifiers, games, and inductive definitions;Aczel,1975
2. Partition theorems and ultrafilters;Baumgartner;Trans. Amer. Math. Soc.,1978
3. Orderings of ultrafilters;Blass,1970
4. The Rudin-Keisler ordering of P-points;Blass;Trans. Amer. Math. Soc.,1973
5. Amalgamation of non-standard models of arithmetic;Blass;J. Symbolic Logic,1977