Mehlhorn, Kurt Algorithms and Complexity, MPI for Informatics, Max Planck Society;
Näher, Stefan Algorithms and Complexity, MPI for Informatics, Max Planck Society;
Mehlhorn, K., & Näher, S. (1990). Bounded ordered dictionaries in $O(\log \log n)$ time and $O(n)$ space. Information Processing Letters, 35, 183-189.