1. Abolpour KH, Zahedi MM (2012) Isomorphism between two BL-general fuzzy automata. Soft Comput 16(4):729–736
2. Birkhoff G (1984) Lattice theory. American Mathematical Society, Providence
3. Bozapalidis S, Bozapalidoy OL (2010) Fuzzy tree language recognizability. Fuzzy Sets Syst 161:716–734
4. Comon H, Dauchet M, Gilleron R, Jacquemard F, Lugiez D, Loding C, Tison S, Tommasi M (2007) Tree automata: technigues and applications.
http://tata.gforge.inria.fr
5. Doner JE (1965) Decidability of the weak second-order theory of two successors. Not Am Math Soc 12:365–468