The four reference materials, as Certified Reference Materials(CRMs), had been approved by State Bureau of Technical Suppervision in 1997. The serial numbers are GBW07295, GBW07296, GBW07315 and GBW07316 respectively.

• 这4个标准物质已于1997年被国家技术监督局批准为国家一级标准物质，序号分别为GBW07295，GBW07296，GBW07315和GBW0731。