count the birthplaces of recepients of the blood-horse magazine list of the top 100 racehorses of the 20th century .
SELECT DISTINCT COUNT attr_open var_uri attr_close where brack_open var_x dbo_honours dbr_Blood-Horse_magazine_List_of_the_Top_100_Racehorses_of_the_20th_Century sep_dot var_x dbo_birthPlace var_uri sep_dot var_uri a dbo_Place brack_close