return me the total citations of the papers containing keyword " Natural Language "
SELECT SUM ( t3.citation_num ) FROM publication_keyword AS t2 JOIN keyword AS t1 ON t2.kid  =  t1.kid JOIN publication AS t3 ON t3.pid  =  t2.pid WHERE t1.keyword  =  "Natural Language";
SELECT SUM ( t3.citation_num ) FROM publication_keyword AS t2 JOIN keyword AS t1 ON t2.kid  =  t1.kid JOIN publication AS t3 ON t3.pid  =  t2.pid WHERE t1.keyword  =  "Natural Language";
[{'SUM ( t3.citation_num )': None}]