John Kennedy actually said...
I have made the determination regarding the ad valorem equivalent of the specific rate of duty (or combination of rates including a specific rate), and regarding the representative period, under the authority of section 350(a) (3) (D).
Context
Proclamation 3479—Carrying Out Certain Agreements Negotiated at the 1960-61 Tariff Conference and Modifying and Terminating...
06/19/1962