The gross estate of a resident shall include property specified in §67-8-303(a)(1), and the gross estate of a nonresident shall include property specified in §67-8-303(a)(2) transferred by the decedent by deed of trust in which the decedent reserved to the decedent, alone or in conjunction with others, powers of revocation, alteration or amendment, upon the exercise of which such property would revert to the decedent, to the extent of the value of such property subject to such powers and with respect to which such powers remained unexercised.