made, special use valuation is not available to the estate.” Id. Here Grimes’s widow, the estate’s executrix, did not attach the recapture, agreement to the estate tax return, as required by Prussner and the applicable regulation, when the return was filed on September 24, 1981. In fact, her attorney did not forward the agreement to the Internal Revenue Service until 10 days after the due date for filing the return. Therefore the executrix did not comply with either Section 2032A(d)(l) of the Internal Revenue Code or with the Treasury Regulation giving effect to the filing requirement. 26 C.F.R. § 20.2032A-8(a)(3). Courts have repeatedly upheld the validity of this Estate Tax Regulation. Prussner, 896 F.2d at 225; McDonald v. Commissioner, 853 F.2d 1494, 1496 n. 3 (8th Cir.1988) (<HOLDING>), certiorari denied sub nom. Cornelius v.
holding that perfection not required for regulation to be reasonable courts task is simply to determine whether regulation is reasonably related to agencys statutory mandate recognizing that the regulation was drafted pursuant to direct statutory authority holding that where a regulation could not fairly be read to have spoken at all on an issue an agencys proposed interpretation of the regulation as it pertained to that issue was not a reasonable interpretation of the regulation recognizing that acts made in violation of statutory authority are void holding that the challenge to a university regulation was moot because the regulation had been substantially amended