Sources for forward and backward citations include the following:
| Source | Description |
|---|---|
| CH2 | Revealed during PCT Chapter 2 (preliminary examination) |
| SUP | Originates from Supplementary Search Report |
| ISR | Originates from International Search Report |
| APP | Cited by the applicant |
| SEA | Originates from the Search Report |
| 115 | Article 115 (observation by third parties) |
| EXA | Revealed during the Examination phase (citing document is kind-code "A") |
| OPP | Revealed during the Opposition phase (only for B2 publications) |
| PRS | Origin Pre-Grant/Pre-Search (beginning week 13 of 2012 for US-A1 pre-grants) |
| APL | Filed for appeal by applicant/proprietor/patentee |
| FOP | Filed for opposition by any third party |
| TPO | Third party observation |
| UNKNOWN | Unknown source |