which silver medalist of the athletics at the 2004 summer olympics – women's 400 metres was also the flagbearer of the mexico at the 2003 pan american games
SELECT DISTINCT var_uri where brack_open dbr_Athletics_at_the_2004_Summer_Olympics_–_Women's_400_metres dbo_silverMedalist var_uri sep_dot dbr_Mexico_at_the_2003_Pan_American_Games dbp_flagbearer var_uri brack_close