| Challenges for open access journals: quantity, quality and economic sustainability | 12 |
| 11 / 2012 | 12 / 2012 | 01 / 2013 | 02 / 2013 | 03 / 2013 | 04 / 2013 | 05 / 2013 | |
| Challenges for open access journals: quantity, quality and economic sustainability | 3 | 0 | 0 | 0 | 0 | 2 | 2 |
| 1 | Russian Federation | 3 |
| 2 | United States of America | 3 |
| 3 | China | 1 |
| 4 | Spain | 1 |
| 5 | Hong Kong | 1 |
| 6 | Indonesia | 1 |
| 7 | Nigeria | 1 |
| 8 | Taiwan | 1 |
| 1 | Atherton | 1 |
| 2 | Barcelona | 1 |
| 3 | Central District | 1 |
| 4 | Pekanbaru | 1 |
| 5 | Santa Clara | 1 |
| 6 | Saratov | 1 |
| 7 | Sayreville | 1 |
| 8 | Taipei | 1 |
| 9 | Tianjin | 1 |