CREATE TABLE inst (instid NUMBER, name CLOB, country CLOB)
CREATE TABLE papers (paperid NUMBER, title CLOB)
CREATE TABLE authorship (authid NUMBER, instid NUMBER, paperid NUMBER, authorder NUMBER)
CREATE TABLE authors (authid NUMBER, lname CLOB, fname CLOB)

Retrieve the country that has published the most papers.
SELECT t1.country FROM inst AS t1 JOIN authorship AS t2 ON t1.instid = t2.instid JOIN papers AS t3 ON t2.paperid = t3.paperid GROUP BY t1.country ORDER BY COUNT(*) DESC LIMIT 1
SELECT "t1"."country" FROM "inst" "t1" JOIN "authorship" "t2" ON "t1"."instid" = "t2"."instid" JOIN "papers" "t3" ON "t2"."paperid" = "t3"."paperid" GROUP BY "t1"."country" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY