Kanovei Vladimir and Reeken Michael, Internal approach to external sets and universes, Part 1, Bounded set theory, Studia logica, vol. 55 (1995), pp. 229–257.Kanovei Vladimir and Reeken Michael, Internal approach to external sets and universes, Part 2, External universes over the universe of bounded set theory, Studia logica, vol. 55 (1995), pp. 347–376.Kanovei Vladimir and Reeken Michael, Internal approach to external sets and universes, Part 3, Partially saturated universes, Studia logica, vol. 56 (1996), pp. 293–322.