The issues are "Navies and fishing rights on the Great Lakes".
Hope this helps !
Photon
<span>The 17th century saw Sweden as an European "Great Power" and one of the major military and political combatants on the continent during the Thirty Years' War. By mid-century, the kingdom included part of Norway, all of Finland and stretched into Russia. Sweden's control of portions of modern Poland, Latvia, Estonia, Lithuania and Germany made the Baltic Sea essentially a Swedish lake.</span>
It spread to China and became popular
Checks and balances is the answer to this question.
