1. C. C. CHANG H. J. KEISLER Model theory. North-Holland, 1973
2. H. J. KEISLER Model theory for infinitary logic. North-Holland, 1971
3. “First order predicate logic with generalized quantifiers.”;LINDSTRÖM;Theoria, vol. Theoria,1966
4. “On extensions of elementary logic.”;LINDSTRÖM;Theoria, vol. Theoria,1969
5. P. LINDSTRÖM “A characterization of elementary logic.” Modality, morality, and other problems of sense and nonsense. Lund, 1973 189 191