第一手来源是被认为是最可靠的研究和验证的信息来源。

In order to use primary source in our research we have to think specifically on our subject and its target.

youdao

第一手来源是被认为是最可靠的研究和验证的信息来源。

In order to use primary source in our research we have to think specifically on our subject and its target.

youdao