Article 5.2(b) provides that the rule in Article 5.2(a) will apply in the case of certain employees who are sent by an employer in the United States to work for a subsidiary or other affiliate of that employer in Norway.  U.S. law permits American companies to extend U.S. Social Security coverage to U.S. citizens and resident aliens employed by an affiliated company in another country.  To do this, the company in the United States must enter into an agreement with the Internal Revenue Service (IRS) to pay Social Security contributions on behalf of all U.S. citizens and residents employed by the foreign affiliate.  Under Article 5.2(b), U.S. citizens or resident aliens who are sent by an American employer to work for a foreign affiliated company in Norway for 5 years or less will continue to be covered by the United States and exempt from Norwegian coverage and contributions, provided the affiliate is covered by an IRS agreement.