N.Y. Comp. Codes R. & Regs. tit. 20 § 139.1
Tax Law, § 639(a)
A nonresident estate or trust's taxable income includes its share of Federal distributable net income, after taking into consideration any applicable New York modifications, to the extent that such share is from New York State sources (see Part 138 of this Article). The adjusted gross income of a nonresident beneficiary of any resident or nonresident estate or trust includes his share of Federal distributable net income, after taking into consideration any applicable New York modifications, to the extent that his share is from New York State sources (see section 132.1 of this Article). The taxable shares described in this section must be determined in the manner described in sections 139.2 through 139.5 of this Part.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 139.1