中华人民共和国国家标准
NATIONAL
STANDARD OF THE PEOPLE'S REPUBLIC OF CHINA
GB/T 20939-2007
Structuring principles for technical products and technical product documentation - Letter codes - Main classes and subclasses of objects according to their purpose and task 技术产品及技术产品文件结构原则 字母代码 按项目用途和任务划分的主类和子类
Issued Date:2007-04-30
Implemented Date:2008-01-01
Issued by:
The Standardization Administration of the People's Republic of China