# EPUBCheck OPF-066: Missing dc:source or source-of…

Source: https://epublab.com/epubcheck/opf-066/ (updated 2026-11-03)

EPUBCheck OPF-066 is an error message: “Missing "dc:source" or "source-of" pagination metadata. The pagination source must be identified using the "dc:source" and "source-of" properties when the content includes page break markers.” The content marks print page breaks but the metadata does not say which print edition the page numbers come from.

- Official message (EPUBCheck 5.4.0): Missing "dc:source" or "source-of" pagination metadata. The pagination source must be identified using the "dc:source" and "source-of" properties when the content includes page break markers.
- Default severity: Error

## Typical causes

- Page-break markers or a page list added without identifying the source edition.

## How to fix it

- Identify the source with dc:source and refine it with source-of, for example <dc:source id="src">urn:isbn:…</dc:source> and <meta refines="#src" property="source-of">pagination</meta>.

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