Here's why:
* Appendix references are supplementary. They are not essential to the core argument or discussion of the main research paper. They are included to provide further information or support for specific points made in the appendix itself.
* Main reference list is for cited sources. The main reference list is for all sources directly cited within the body of the paper. These sources are directly relevant to the argument and research.
* Avoiding redundancy. Including appendix references in the main list creates unnecessary repetition and can make the list confusing for the reader.
However, there are exceptions:
* If an appendix reference is also cited in the main body of the paper, it should be included in the main reference list. This ensures that the source is properly acknowledged and can be easily found by the reader.
* If the appendix is a separate document that is meant to be read independently, it may have its own reference list. This is particularly true if the appendix contains extensive references that are not directly related to the main body of the paper.
In general, it's best to keep the main reference list focused on the sources cited within the body of the paper. This makes it easier for readers to find the information they need. Appendix references should be treated as a separate list, if needed, and clearly labeled as such.