(a) General. — The West Virginia source income of a nonresident individual shall be the sum of the net amount of income, gain, loss and deduction entering into his or her federal adjusted gross income, as defined in the laws of the United States and section nine of this article, for the taxable year, derived from or connected with West Virginia sources, including:
(1) His or her distributive share of partnership income, gain, loss and deduction, determined under section thirty-seven; and