Ronald Jensen, Definable Sets of Minimal DegreeMathematical Logic and Foundations of Set Theory, Proceedings of an International Colloquium Held Under the Auspices of The Israel Academy of Sciences and Humanities. ,vol. 59, pp. 122- 128 ,(1970) , 10.1016/S0049-237X(08)71934-7
Azriel Levy, Definability in Axiomatic Set Theory IIMathematical Logic and Foundations of Set Theory, Proceedings of an International Colloquium Held Under the Auspices of The Israel Academy of Sciences and Humanities. ,vol. 59, pp. 129- 145 ,(1970) , 10.1016/S0049-237X(08)71935-9
R.B. Jensen, R.M. Solovay, Some Applications of Almost Disjoint SetsMathematical Logic and Foundations of Set Theory, Proceedings of an International Colloquium Held Under the Auspices of The Israel Academy of Sciences and Humanities. ,vol. 59, pp. 84- 104 ,(1970) , 10.1016/S0049-237X(08)71932-3