EXHIBIT 99.1
JOINT FILING AGREEMENT
Each of the undersigned hereby agrees that this Amendment No. 22 to the statement on Schedule 13D is being filed with the United States Securities and Exchange Commission on behalf of each of the undersigned pursuant to Rule 13d-1(k) under the United States Securities Exchange Act of 1934, as amended.
Dated: May 13, 2019
| Glencore AG | ||
| By: | /s/Nicola Leigh | |
| Name: | Nicola Leigh | |
| Title: | Authorized Signatory | |
| By: | /s/Patrick Huber | |
| Name: | Patrick Huber | |
| Title: | Authorized Signatory | |
| Glencore International AG | ||
| By: | /s/Martin Haering | |
| Name: | Martin Haering | |
| Title: | Officer | |
| By: | /s/Peter Friedli | |
| Name: | Peter Friedli | |
| Title: | Officer | |
| Glencore plc | ||
| By: | /s/John Burton | |
| Name: | John Burton | |
| Title: | Company Secretary | |
