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Note 9 - Income Taxes (Details Textual) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2019
Effective United States Tax on U.S. Source Shipping 2.00%   4.00%
Effective Tax on U.S. Source Shipping, Amount $ 19,726 $ 15,135