Nivat, Maurice Programming Logics, MPI for Informatics, Max Planck Society;
Podelski, Andreas Programming Logics, MPI for Informatics, Max Planck Society;
Nivat, M., & Podelski, A. (1997). Minimal Ascending and Descending Tree Automata. SIAM Journal on Computing, 26(1), 39-58. doi:10.1137/S0097539789164078.