list all the collaborators of the artist which has collaborated with the presidents of the united states of america ?
SELECT DISTINCT var_uri where brack_open var_x dbo_associatedMusicalArtist dbr_The_Presidents_of_the_United_States_of_America_ attr_open band attr_close sep_dot var_x dbo_associatedMusicalArtist var_uri sep_dot var_x a dbo_Artist brack_close