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Other Long-Term Liabilities
 12 Months Ended
Dec. 31, 2018
Other Liabilities Disclosure [Abstract]  
Other Long-Term Liabilities

7. OTHER LONG-TERM LIABILITIES

Other long-term liabilities and deferred credits on the balance sheet consisted of:

 

   December 31, 
   2018   2017 
   (thousands of dollars) 
Royalties payable (1)  $500   $500 
   $500   $500 

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(1)Royalties payable were derived during prior years of production. Liabilities do not accrue interest or have a stated maturity date.