670.54. If the supplies referred to in sections 670.52 and 670.53 are made to two or more individuals, a reference in those sections to a particular person is to be read as a reference to all of those individuals as a group, but, in the case of a rebate under subparagraph 1 of the first paragraph of section 670.53, only the individual who applied for the rebate under sections 370.0.1 to 370.4 may apply for the rebate under that subparagraph.