Good things, interests specify the source 1 Posts:

• To acknowledge the source for providing useful information
• Include additional information for readers who want to read more
• Make skeptical readers believe that the article is correct
• So that other writers can quickly check the article, especially in cases of covert sabotage
• Avoid and resolve revision discussions
• Avoid situations where others accuse you of plagiarism or not telling the truth
• Search, Correct information easily when necessary

How to write annotations:

Specify the author, Link to the article you copied or referenced (If you have any corrections or additions) at the beginning or end of your article.

Source & refer in wikipedia.org