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FAIR VALUE OF FINANCIAL INSTRUMENTS - UNL's Securities Fair Value Hierarchy (Details) - USD ($)
Jun. 30, 2020
Dec. 31, 2019
United States [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value $ (157,130) $ (435,678)
Short-Term Investments [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value 4,339,265 3,289,117
Fair Value, Inputs, Level 1 [Member] | United States [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value (157,130) (435,678)
Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value 4,339,265 3,289,117
Fair Value, Inputs, Level 2 [Member] | United States [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value 0 0
Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | United States [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member]    
FAIR VALUE OF FINANCIAL INSTRUMENTS    
Securities, fair value $ 0 $ 0