1. Yaniv Bargury. The Hierarchy of Transitive Closure Master thesis, Department of Computer Science, Technion—Israel Institute of Technology, Haifa, (In preparation).
2. J. R. Büchi. Weak second-order arithmetic and finite automata Z. Math. Logik Grundlagen Math 6, 66–92, 1960.
3. Ariel Calò. The Expressive Power of Transitive Closure Master thesis, Department of Computer Science, Technion—Israel Institute of Technology, Haifa, 1990.
4. Ariel Calò and J.A. Makowsky, The expressive power of transitive closure, to appear in the proceedings of the Symposium on Logical Foundations of Computer Science ‘Logic at Tver '92', Lecture Notes in Computer Science, 1992.
5. W. Coy, Automata in Labyrinths Fundamentals of Computation Theory, LNCS 56, 65–71, 1977.