(i) Purchase price. Intangible assets described in 1.897-1(f)(1)(ii) that were acquired by purchase from a person not related to the purchaser within the meaning of 1.897-1(i) may be valued at their purchase price. However, such purchase price must be adjusted to reflect any amortization required by generally accepted accounting principles applied in the United States. Intangible assets acquired by purchase shall include any amounts allocated to goodwill or going concern valued pursuant to section 338(b)(3) and regulations thereunder. Intangible assets acquired by purchase shall not include assets that were acquired indirectly through an acquisition of stock to which section 338 does not apply. Such assets must be value pursuant to a method described in subdivision (ii) or (iii) of this paragraph (o)(4).