select pno
from   parts p
where  not exists (
  select cno
  from   customers c, zipcodes z
  where  c.zip = z.zip and
         z.city='Wichita' and not exists (
    select o.ono
    from   orders o, odetails od
    where  o.ono = od.ono and
           od.pno = p.pno and
           o.cno = c.cno));
