1870-199X 1870-199X S1870-199X2007000200063 10.22201/fo.1870199xp.2007.11.2.15868 Mexico Mexico Mexico Mexico Mexico 00 00 2007 00 00 2007 11 2 63 69

1. 2000 Chicago, IL 2. 1981 2 90-9 3. 1994 1 105-12 4. 2002 5. 1974 2 64-72 6. 1999 115 448-60 7. 1992 89 1 8. 1995 96 825-40 9. 1998 34 1-30 10. 1997 100 852-61 11. 1998 12. 1972 61 1-28 13. 1987 21 448-65 14. 1966 15. 2003 16. 2001 120 149-53 17. 1999 5 3-8 18. 2001 19. 1985 75 328-37 20. 1995 14 93-7