N.Y. Comp. Codes R. & Regs. tit. 20 § 138.3
Tax Law, § 638(a)(2)
In determining the New York taxable income of a nonresident estate or trust, there must be added or subtracted, as the case may be, any other items of income, gain, loss or deduction of the estate or trust recognized for Federal income tax purposes but which are not reflected in distributable net income as provided in section 138.2 of this Part, to the extent such items are derived from or connected with New York State sources as determined in accordance with the applicable rules of Part 132 of this Article as in the case of a nonresident individual. All such items of income or gain must also be increased or decreased, as the case may be, by the amount of any of the applicable modifications described in section 138.4 of this Part.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 138.3