I'm using Word 2013, and I'm writing the thesis.
In the table of contents, I would like for some items, such as references, to appear without the page number.
I deleted the page number and then updated the table of contents, this reappears.

How can I fix?

To make sure the items you want without page numbers, format those with another style not included to compile the TOC. If you wanted those items without the page numbers to appear with the TOC, simple insert/tabulate them immediately following the TOC.