In Europe, requirements for practicing as patent attorney before national patent offices differ from those needed for practicing before the European Patent Office (EPO). On the national level, the requirements are not harmonized across the European Union, except that the EU makes sure that respective professional qualifications are mutually recognized to some degree. In the United States, the patent attorney must pass a special examination to test his knowledge of patent office procedures. Some countries allow lawyers who are not citizens to practice. Some countries will allow lawyers from a second country to make filings if the second country will do the same for lawyers from that first country. Many times, a patent attorney from a foreign country will work with a local attorney to make sure that the patent application for that country is filed correctly and quickly.