instruction: how many papers did nicola dell and Brian DeRenzi write together
response: SELECT DISTINCT COUNT(1) FROM author AS AUTHOR_0, author AS AUTHOR_1, writes AS WRITES_0, writes AS WRITES_1 WHERE AUTHOR_0.authorname = 'nicola dell' AND AUTHOR_1.authorname = 'Brian DeRenzi' AND WRITES_0.authorid = AUTHOR_0.authorid AND WRITES_1.authorid = AUTHOR_1.authorid AND WRITES_1.paperid = WRITES_0.paperid