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The codebook is provided by ICPSR as a Portable Document Format (PDF) file. The PDF file format was developed by Adobe Systems Incorporated and can be accessed using PDF reader software, such as the Adobe Acrobat Reader. Information on how to obtain a copy of the Acrobat Reader is provided on the ICPSR Web site.本数据集的代码簿由ICPSR以可移植文档格式（Portable Document Format，简称PDF）文件形式提供。该格式由Adobe系统公司（Adobe Systems Incorporated）开发，可通过PDF阅读器软件（如Adobe Acrobat阅读器）打开访问。关于获取Acrobat阅读器副本的相关说明，可在ICPSR官方网站查询。