The file "stem_rules_context_2_UTF-8.txt" does not contain the same rules as the original "stem_rules_context_2.txt" file from http://lml.bas.bg/~nakov/bulstem/ . It is in fact composed of all three original rule files. Could you rename the file "stem_rules_context_2_UTF-8.txt" to eg. "stem_rules_context_2_3_1_UTF-8.txt" to avoid confusion?