These references tell you where the current text (or its view) comes from. According to these tips, look at the references at the back of the paper, and you will know where it was published and what articles were published.

(Nord, 2000) is an article published by Nord in 2000;

(Wu, Cheng Zhenqiu, 200 1: 1752) is an article published by these two authors on 200 1, and the position of the quoted paragraphs in this journal or works is on page 1752;

(1997: 1 186) is the aforementioned author, and here is the page 1 186 of the author's 1997 document.

As long as a formal paper quotes other people's words or opinions, it is necessary to indicate the source. The article you see uses one of several common methods to mark the source. There are many specific requirements. If you are interested or need to work, you can read some books about paper format.