In times of political upheaval, the union radio stations would become the only trustworthy source of information. As the military captured newspapers, radio and TV stations in the capital and other cities, the only information available would come from the miners' radio stations. They would join the "cadena minera" ("mining chain") until the army penetrated the mining camps and mounted an assault on the stations, which were defended (sometimes to the death) by the workers. A film by Bolivian filmmaker Jorge Sanjinés, "The Courage of the People", reenacts the attack on the mining district of Siglo XX by the army in June 1967. Another film, a documentary by Alfonso Gumucio Dagron and Eduardo Barrios entitled "Voices of the Mine" and produced by UNESCO, describes their political and social importance.