Ok, at this point I can try the filters and other possibilities of biblatex. It works and now I can play with it!
If somebody wants to read an abstract in Spanish language about my problem with multiples bibliographies in LyX I'm going to write it in this page: http://www.macuarium.com/foro/index.php?showtopic=295047&st=0#entry2312847 Best regards Antonio Díaz
