I.R.C. Section 3121(b)(19)
26 USC Sec. 3121(b)(19) 01/06/97 TITLE 26 - INTERNAL REVENUE
CODE Subtitle C - Employment Taxes CHAPTER 21 - FEDERAL INSURANCE CONTRIBUTIONS
ACT Subchapter C - General Provisions
-STATUTE-
(b) Employment For purposes of this chapter, the term ''employment'' means
any service, of whatever nature, performed (A) by an employee for the person
employing him, irrespective of the citizenship or residence of either, (i)
within the United States, or (ii) on or in connection with an American vessel
or American aircraft under a contract of service which is entered into within
the United States or during the performance of which and while the employee
is employed on the vessel or aircraft it touches at a port in the United States,
if the employee is employed on and in connection with such vessel or aircraft
when outside the United States, or (B) outside the United States by a citizen
or resident of the United States as an employee for an American employer (as
defined in subsection (h)), or (C) if it is service, regardless of where or
by whom performed, which is designated as employment or recognized as equivalent
to employment under an agreement entered into under section 233 of the Social
Security Act; except that such term shall not include -
(19) Service which is performed by a nonresident alien individual for the
period he is temporarily present in the United States as a nonimmigrant under
subparagraph (F), (J), (M), or (Q) of section 101(a)(15) of the Immigration
and Nationality Act, as amended, and which is performed to carry out the purpose
specified in subparagraph (F), (J), (M), or (Q), as the case may be;