1. Beth's Theorem fails in L<ω;Badger;Notices AMS, A-322,1974
2. Infinitary logic and admissible sets;Barwise;JSL,1969
3. Absolute logics and L∞ω;Barwise;Ann. Math. Logic,1972
4. Axioms for abstract model theory;Barwise;Ann. Math. Logic,1974
5. Admissible sets and structures;Barwise,1957