count all the books written by an author buried in the third addition to rockville and old st . mary's church and cemetery ?
SELECT DISTINCT COUNT attr_open var_uri attr_close where brack_open var_x dbo_restingPlace dbr_Third_Addition_to_Rockville_and_Old_St._Mary's_Church_and_Cemetery sep_dot var_uri dbo_author var_x sep_dot var_uri a dbo_Book brack_close