1. Infinitary logic and admissible sets;Barwise;J. Symb. Logic,1969
2. J. Barwise, Back and forth thru infinitary logic, to appear.
3. Hanf numbers for fragments of L∞ω;Barwise;Israel J. Math.,1971
4. Completing theories by forcing;Barwise;Ann. Math. Logic,1970
5. Persistent and invariant formulas relative to theories of higher order;Feferman;Bull. Amer. Math. Soc.,1966