What are all the countries?
select country from inst
How many papers did each of them publish?
select country, count(*) 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
Which country published the most?
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