If you are using the wiki-code editor, you may find that your references are disappearing due to an unclosed template, like {{Cite Book}}. The problem may also be cause by an unclosed reference tag when re-using the citation. If we've named a citation "nytimes1989" and we re-use it as <nytimes1989>, the page expects a closing tag <nytimes1989/> just like when we have pairs of tags (<ref>...</ref> ) the last tag must be closed.
If you are using the wiki-code editor, you may find that your references are disappearing due to an unclosed template, like {{Cite Book}}. The problem may also be cause by an unclosed reference tag when re-using the citation. If we've named a citation "nytimes1989" and we re-use it as <nytimes1989>, the page expects a closing tag <nytimes1989/> just like when we have pairs of tags (<ref>...</ref> ) the last tag must be closed.