It was written by an unknown author.

该书的作者是匿名的。

youdao

What if a book has an unknown publication date, or more than one author?

如果一本书有一个未知的出版日期，或者有多个作者，怎么办？

youdao

Often, when I am reading a good book, I stop and thank my teacher. That is, I used to, until she got an unlisted number. ~ Author unknown.

每当我阅读一本好书，总会停下来感谢我的老师。更确切地说，我过去常这么做，直到她换了电话号码，号码簿中找不到。

youdao

This quote from an unknown author might be the most apt description of my life as an entrepreneur.

FORBES: Why Big Questions And Bad Decisions Make Better Entrepreneurs

Marketing a genre-defying book by an unknown Dutch author could prove challenging.

WSJ: Dutch Thriller Is a Surprise Global Hit

So Alexander Kravtsov, the author of the city charter, may lose votes to a namesake who is an unknown student.

ECONOMIST: Russia