Question: What are the lname and fname of all authors that wrote exactly 1 paper?
SQL: SELECT t1.lname,t1.fname FROM authors AS t1 JOIN authorship AS t2 ON t1.authid   =   t2.authid JOIN papers AS t3 ON t2.paperid   =   t3.paperid 
group by t1.authID  having count ( * )   = 1