She spent weeks in the library tracking down all the reference information on the subject.

她花了好几周在图书馆里查找关于这个课题的所有参考资料。

youdao

She spent weeks in the library tracking down all the reference information on the subject.

她花了好几周在图书馆里查找关于这个课题的所有参考资料。

youdao