(d)to any person or association of persons from assets transferred directly or indirectly, otherwise than for adequate consideration to the person or association of persons by such individual, to the extent to which the income from such assets is for the immediate or deferred benefit of his or her spouse or his son's wife, as the case may be, other than the assets transferred before 1st June 1973, to the extent to which the income from such assets is for the immediate or deferred benefit of his son's wife.