Quarterly report pursuant to Section 13 or 15(d)

Note 3 - Revenue From Contracts With Customers - Changes in Contract Liabilities (Details)

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Note 3 - Revenue From Contracts With Customers - Changes in Contract Liabilities (Details) - USD ($)
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Total deferred revenue, beginning of period $ 700,000 $ 700,000
Revenue recognized from satisfaction of performance obligations
Total deferred revenue, end of period $ 700,000 $ 700,000