New York Laws
Part 3 - Nonresidents and Part-Year Residents
633 - New York Source Income of a Nonresident Estate or Trust.

(1) The net amount of items of income, gain, loss and deduction
entering into federal adjusted gross income, as determined under
paragraph four of subsection (e) of section six hundred one, derived
from or connected with New York sources. Such determination of source
shall be made in accordance with the applicable rules of section six
hundred thirty-one as in the case of a nonresident individual.
(2) The portion of the modifications described in section six hundred
eighteen which relate to income derived from New York sources other than
that portion of the modification provided in subsection three thereof
which relates to section six hundred fifteen.
(b) Special New York source rules. Deductions with respect to capital
losses, passive activity losses and net operating losses shall be based
solely on income, gains, losses and deductions derived from or connected
with New York sources, under regulations of the tax commission, but
otherwise determined in the same manner as the corresponding federal
deductions.