Amortization of intangible assets that relate to past acquisitions will recur in future periods until such intangible assets have been fully amortized. Any future acquisitions may result in amortization of additional intangible assets. Base tax rate is defined as the effective tax rate excluding the impacts of foreign exchange gains (losses), non-operating benefits, net, amortization of intangibles as of the Separation from DowDuPont, and significant items (including goodwill impairment charges). All periods for the first quarter of 2019 and prior are on a pro forma basis as discussed above in the paragraph 'Corteva Unaudited Pro Forma Financial Information'.