| Date | Value |
|---|---|
| Jan 24, 2014 17:08 | 350 ppm |
| Jan 16, 2014 14:28 | 350 ppm |
| Jan 9, 2014 15:30 | 340 ppm |
| Jan 2, 2014 15:46 | 340 ppm |
| Dec 12, 2013 15:46 | 360 ppm |
| Nov 29, 2013 15:46 | 380 ppm |
| Nov 11, 2013 15:46 | 360 ppm |
| Oct 23, 2013 17:14 | 360 ppm |
| Sep 30, 2013 13:17 | 360 ppm |
| Sep 9, 2013 13:14 | 350 ppm |
| Aug 28, 2013 17:26 | 390 ppm |
| Jul 26, 2013 16:53 | 425 ppm |