1. Lennart Åqvist, A New Approach to the Logical Theory of Interrogatives, Part I: Analysis, Uppsala 1965.
2. Emmon Bach and Robert T. Harms (eds.), Universals in Linguistic Theory, Holt, Rinehart and Winston, New York 1968.
3. C. Leroy Baker, ?Definiteness and Indefiniteness in English?, University of Illinois master's thesis, 1966.
4. C. Leroy Baker, Indirect Questions in English, University of Illinois doctoral dissertation, 1968.
5. C. Leroy Baker, ?Double Negatives?, Linguistic Inquiry (1970).