Indicators, recursive saturation and expandability L. Kirby, K. McAllon, R. Murawski (1981) Fundamenta Mathematicae
Indiscernibles in the alternative set theory Antonín Sochor, Alena Vencovská (1981) Commentationes Mathematicae Universitatis Carolinae
Initial segments and isomorphic images of nonstandard models of arithmetic A. Ignjatović (1986) Matematički Vesnik