以下为句子列表：
英文: Before conducting regular sampling surveys, it is necessary to find out about the basic statistics units and their geographical distribution and to establish a scientific sampling framework in accordance with an approved plan for sampling surveys.
中文: 进行经常性抽样调查，应当在调查前查明基本统计单位及其分布情况，按照经批准的抽样调查方案，建立科学的抽样框。
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