discussed Cited "see, e.g." United States v. Crawford See also United States v Henderson, 298 F2d 522, 525 (CA 7th Cir) (1962), cert den 369 US 878 , 8 L ed 2d 280, 82 S Ct 1150 (1962), in which the Court of Appeals for the Seventh Circuit described the rule as prohibiting exclusion of a substantial group on the basis of “irrational or self-imposed standards.” A method of selection which uses criteria reasonably and rationally calculated to obtain jurors meeting the statutory requirements for service is proper.