Retrieve the title of the paper that has the largest number of authors.
SELECT t2.title FROM authorship AS t1 JOIN papers AS t2 ON t1.paperid  =  t2.paperid WHERE t1.authorder  =  (SELECT max(authorder) FROM authorship)
title of the paper that has the largest number of authors refers to MAX(authorder) in the authorship table and joining it with the papers table to get the title;