Alma Isabel Martinez Oscar Castillo Mario Garcia Comparative Study of Type-1 and Type-2 Fuzzy Systems Optimized by Hierarchical Genetic Algorithms. 53-70 2008 Soft Computing for Hybrid Intelligent Systems http://dx.doi.org/10.1007/978-3-540-70812-4_4 series/sci/2008-154 db/series/sci/sci154.html#MartinezCG08