what keyphrase does Brian DeRenzi write about that gets most citations ?
SELECT DISTINCT t1.keyphrasename  ,  SUM ( t3.numcitedby ) FROM paperkeyphrase AS t2 JOIN keyphrase AS t1 ON t2.keyphraseid  =  t1.keyphraseid JOIN paper AS t3 ON t3.paperid  =  t2.paperid JOIN writes AS t4 ON t4.paperid  =  t3.paperid JOIN author AS t5 ON t4.authorid  =  t5.authorid WHERE t5.authorname  =  "Brian DeRenzi" GROUP BY t1.keyphrasename ORDER BY SUM ( t3.numcitedby ) DESC;
SELECT DISTINCT t1.keyphrasename  ,  SUM ( t3.numcitedby ) FROM paperkeyphrase AS t2 JOIN keyphrase AS t1 ON t2.keyphraseid  =  t1.keyphraseid JOIN paper AS t3 ON t3.paperid  =  t2.paperid JOIN writes AS t4 ON t4.paperid  =  t3.paperid JOIN author AS t5 ON t4.authorid  =  t5.authorid WHERE t5.authorname  =  "Brian DeRenzi" GROUP BY t1.keyphrasename ORDER BY SUM ( t3.numcitedby ) DESC;
[{'Nenhum': 'Nenhum resultado encontrado'}]