ESSENTIAL
| Date | Clue |
|---|---|
| 2015-03-01 | Required |
| 2013-12-21 | Like many nutrients |
| 2012-06-03 | Required |
| 2009-04-04 | Hardly necessary |
| 2000-05-18 | Hardly extraneous |
| Date | Clue |
|---|---|
| 2015-03-01 | Required |
| 2013-12-21 | Like many nutrients |
| 2012-06-03 | Required |
| 2009-04-04 | Hardly necessary |
| 2000-05-18 | Hardly extraneous |