1. Axioms for abstract model theory;Barwise, K. Jon;Ann. Math. Logic,1974
2. Back and forth through infinitary logic;Barwise, Jon,1973
3. On reduced products and filters;Benda, Miroslav;Ann. Math. Logic,1972
4. C. C. Chang and H. J. Keisler, Model theory, North-Holland, Amsterdam, 1973.
5. Die Grundlehren der mathematischen Wissenschaften, Band 211;Comfort, W. W.,1974