# EPUBCheck RSC-011: Found a reference to a resource that is…

Source: https://epublab.com/epubcheck/rsc-011/ (updated 2026-11-03)

EPUBCheck RSC-011 is an error message: “Found a reference to a resource that is not a spine item.” A hyperlink points to a content document that is in the manifest but not in the spine, so reading apps may not be able to open it.

- Official message (EPUBCheck 5.4.0): Found a reference to a resource that is not a spine item.
- Default severity: Error

## Typical causes

- A note, appendix or answer page linked from the text but never added to the spine.

## How to fix it

- Add the document to the spine. If it should not appear when paging through the book, add it with linear="no".

Message text and severity: EPUBCheck (W3C, BSD-3-Clause). Explanation: EPUBLab.