中国科学院数学与系统科学研究院期刊网
A Theorem on the Existence of Nonprincipal Arithmetical Ultrafilters on ω
Fang Ting WANG
Acta Mathematica Sinica, Chinese Series . 2006, (2): 283 -288 .  DOI: 10.12386/A2006sxxb0036