sentences:  A relatively large number of common criminals released from prison were brought into the mines as well.The Valley was declared a restricted area from 4 August until 1 January 1978.Strict surveillance was intended to block the flow of any information to the rest of the country or contact with the outside world, yet 22 miners acting on behalf of 800 others managed to send a letter (dated 18 September) to the French newspaper "Libération", which published it on 12 October.