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Note 9 - Inventories (Tables)
9 Months Ended
Sep. 30, 2021
Notes Tables  
Schedule of Inventory, Current [Table Text Block]
   

September 30,

   

December 31,

 
   

2021

   

2020

 

Coal

  $ 8,521     $ 7,163  

Supplies

    47,494       49,037  

Total Inventories

  $ 56,015     $ 56,200