The citation source category indicates the relevance of the citation. Values include the following:
| Source Category | Description |
|---|---|
| A | Technological background: defining the state of the art and not prejudicing novelty or inventive step. |
| D | Document cited in the application. |
| E | Earlier patent document, but published on or after the filing date of the application searched. Indicates potentially conflicting patent documents. |
| I | References cited by publications with a publication date of April 2011 or later may have category "I". Category "I" is category "X" further defined: |
| L | Document cited for other reasons. |
| O | Non-written disclosure. |
| P | Intermediate document. |
| R | CN only. Referring to a patent application or a utility model filed on the same day which relates to the same invention. |
| T | Theory or principle underlying the invention. |
| X | Particularly relevant if taken alone. |
| Y | Particularly relevant if combined with another document of the same category. |