Yes, it is usually necessary to mark references in articles. In academic papers, when quoting other people's opinions, research results or data, it should be marked in the corresponding position to indicate the source of this information. This helps to ensure academic integrity and provide accurate reference information for readers.

There are two common marking methods:

1. Author-date system:

When citing other people's research, the author's surname and publication year are used to mark the citation source. This kind of annotation can be used to directly quote sentences in the original text, or to summarize or indirectly quote other people's views. Please refer to the "author-date system" annotation method mentioned earlier for the specific annotation format.

2. Digital system:

When citing other people's research, the citation order is indicated by numbers, and the numbers are put in square brackets. In this way, the documents in the reference list are numbered in sequence, and then the words are marked with corresponding numbers.

No matter what marking method is adopted, it is necessary to provide complete citation information in the reference list of the paper so that readers can find specific documents.

Please note that when marking papers, you should follow the citation norms required by specific academic fields, journals or instructors, and determine a clear and consistent marking style to ensure the academic standardization of papers.