In December 1967, when he arrived at a snowy farm on China’s northeastern border with the Soviet Union, Xu Chenggang carried with him an electron tube to help him assemble a radio. 1967年12月，许成钢来到中国东北中苏边境附近的一座白雪皑皑的农场，当时他带了一个电子管，准备用它组装一个收音机。 Mr. Xu, a 17-year…