1. Real Analysis and Probability;Ash,1972
2. Orderings of ultrafilters;Blass,1970
3. Amalgamation of nonstandard models of arithmetic;Blass;J. Symbolic Logic,1977
4. A model-theoretic view of some special ultrafilters;Blass,1978
5. Ultrafilters on a countable set;Booth;Ann. Math. Logic,1970