William O. Douglas,
International Union v. Wisconsin Employment Relations Board…
“ Section 7 read in conjunction with § 13 must mean that one of the 'concerted activities' in which employees may engage is to strike in these interstate industries. In all of labor's history no 'concerted activity' has been more conspicuous and important than the strike; and none was thought to be more essential to recognition of the right to collective bargaining. Moreover, the strike historically and in the present cases was used to make effective the collectiv bargaining power which § 7 of the Wagner Act guarantees. ”
