What are the paper id of Gibbons?
SELECT DISTINCT paperID FROM authors AS t1 JOIN authorship AS t2 ON t1.authid   =   t2.authid  WHERE t1.lname   =   "Gibbons"
paper id of Gibbons refers to DISTINCT selection from paperID; Gibbons being an author relates to filtering WHERE lname = 'Gibbons'; joining authors and authorship tables on authid;