Armenia, Azerbaijan, Belarus, Georgia, Kyrgyzstan, Moldova, Tajikistan, Turkmenistan, and Uzbekistan (Commonwealth of Independent States or C.S.I) up to 5 years of Tax Treaty

2 years of teaching/research tax treaty with unlimited exemption. 5 years with maximum of 10000 $ exemption using the Tax treaty for recipients of grants, fellowships, scholarships and awards.

Tax treaty for Professors, Teachers, and Researchers
An individual who is a resident of a C.I.S. member on the date of arrival in the United States and who is temporarily in the United States at the invitation of the U.S. Government or an educational or scientific research institution in the United States primarily to teach, engage in research, or participate in scientific, technical, or professional conferences is exempt from U.S. income tax on income for teaching, research, or participation in these conferences for a maximum period of 2 years.

This exemption does not apply to income from research carried on mainly for the benefit of a private person, including a commercial enterprise of the United States or a foreign trade organization of a C.I.S. member.

The exemption does, however, apply if the research is conducted through an intergovernmental agreement on cooperation.

This exemption also applies to journalists and correspondents who are temporarily in the United States for periods not longer than 2 years and who receive their compensation from abroad. It is not necessary that the journalists or correspondents be invited by the U.S. Government or other appropriate institution, nor does it matter that they are employed by a private person, including commercial enterprises and foreign trade organizations.

Tax treaty for Training, education, studying and researchers ecipients of grants, fellowships, scholarships and awards

An individual who is a resident of a C.I.S. member and who is temporarily in the United States primarily to study at an educational or scientific research institution or to obtain training for qualification in a profession or specialty is exempt from U.S. income tax on amounts received as stipends, scholarships, or other substitute allowances necessary to provide ordinary living expenses. An individual is entitled to the benefit of this exemption for a maximum of 5 years and for less than $10,000 in each tax year.

An individual who is a resident of a C.I.S. member and who is temporarily in the United States primarily to acquire technical, professional, or commercial experience or perform technical services and who is an employee of, or under contract with, a resident of a C.I.S. member is exempt from U.S. income tax on the amounts received from that resident. Also exempt is an amount received from U.S. sources, of not more than $10,000, that is necessary to provide for ordinary living expenses. The exemption contained in this paragraph is limited to 1 year.

An individual who is a resident of a C.I.S. member and who is temporarily present in the United States under an exchange program provided for by an agreement between governments on cooperation in various fields of science and technology is exempt from U.S. income tax on all income received in connection with the exchange program for a period not longer than 1 year.

(Reported from Internal Revenue Service (IRS), US government Publication 901)