I am a visiting professor from Hungary. I was in the USA working as a postddoc at UNC Chapel Hill from 2002-2005. During this period I was tax exempt based on the Treaty Article 17 for 2 years. Then I returned to Hungary for the next 5 years, and in 2010 I did a short research program (50 days), same institution, as a visiting professor, also with a J1 visa. Can I claim again the tax treaty benefits for this income?