Plagiarism refers to unauthorized copying of other people's original works, opinions or words and using them in one's own works without quoting or indicating the source. In academic writing and research, plagiarism is a serious violation of academic ethics and norms, and it is also a kind of knowledge theft.

Therefore, references cannot be copied directly. When quoting or drawing lessons from other people's opinions, data or words, the following principles should be followed:

1. Citation: If you want to quote others directly, you need to use quotation marks and indicate the source in the text, including the author's name, publication year, article title, periodical name or book publishing information. At the same time, the detailed information of the cited documents should also be accurately listed in the reference list.

2. Summary: If you want to learn from other people's viewpoints or data, you can summarize or generalize, but you must clearly point out that these contents come from other people's research in the text and quote the original source in the references.

3. Independent expression: try to express opinions, analysis and summary in your own language. Even if you refer to other people's research results, you should express it independently through your own understanding and analysis, and avoid copying other people's sentences or paragraphs directly.

In academic writing, it is very important to quote and indicate the source correctly, which can show your respect for related research and academic integrity. At the same time, it can also let readers know the source of the literature you refer to, so as to further consult the original materials. Therefore, it is suggested that in the process of writing, we should always respect intellectual property rights, follow academic norms, and accurately quote and indicate references.