The unique existential quantifier

J. W. Addison: Some consequences of the axiom of constructibility. Fundamenta Mathematicae, vol. 46 (1959), pp. 337–357.

J. W. Addison and Yiannis N. Moschovakis: Some consequences of the axiom of definable determinateness. Proceedings of the National Academy of Sciences, vol. 59 (1968), pp. 708–712.

S. C. Kleene: Quantification of number-theoretic functions. Compositio Mathematica, vol. 14 (1959), pp. 23–40.

Nicolas Lusin: Les Ensembles Analytiques. Gauthier-Villars, Paris, 1930.

Donald A. Martin: The axiom of determinateness and reduction principles in the analytical hierarchy. Bulletin of the American Mathematical Society, vol. 74 (1968), pp. 687–689.

Dieter Rödding: Anzahlquantoren in der Kleene-Hierarchie. Archiv für mathematische Logik und Grundlagenforschung, vol. 9 (1966), pp. 61–65.

Dieter Rödding: Anzahlquantoren in der Prädikatenlogik. Ibid., pp. 66–69.

Joseph R. Shoenfield: Mathematical Logic. Addison-Wesley, 1967.