Briggs-Darby Construction Company. Nos. 9673-76, in circuit court of appeals for 5th circuit, Briggs-Darby Construction Company v. commissioner of internal revenue; Briggs-Killian Company v. [same]; Briggs-Spence Company v. [same]; W. M. Thornton, Inc., v. [same], on petitions for review of decisions of Board of Tax Appeals; brief for respondent.