Which historical legislators are members of the National Greenbacker party? Write their first and last names.
members of the National Greenbacker party refers to party = 'National Greenbacker'; first and last names refers to first_name, last_name
SELECT T2.first_name, T2.last_name FROM `historical-terms` AS T1 INNER JOIN historical AS T2 ON T2.bioguide_id = T1.bioguide WHERE T1.party = 'National Greenbacker'