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Note 3 - Other Long-term Assets (In Thousands) (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2023
Notes Tables |
Schedule of Other Assets, Noncurrent [Table Text Block] |
|  | December 31, |
|  | 2023 |  |  | 2022 |
Advanced coal royalties |  | $ | 5,521 |  |  | $ | 5,967 |
Other |  |  | 1,540 |  |  |  | 1,618 |
Total other assets |  | $ | 7,061 |  |  | $ | 7,585 |

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