After 1814, external trade policy was essentially focused on trade agreements. Even in the preceding period, trade agreements played an important role in the city's foreign relations, but aside from the treaties with France, there were only attempts and efforts. The foundation of Hamburg's foreign trade relations still consisted of the old privileges and letters of protection or the customs based on them. The pursuit of maintaining these privileges and making them beneficial for Hamburg's trade abroad occupies a significant part of Hamburg's outward-looking policy. In the 19th century, the classic era of trade agreements, Hamburg entered the international trade system created by them. The publishing house of sciences publishes well-known historical literature.