Note 6 - Income Taxes - Reconciliation of Income Tax Provisions (Details) - USD ($)	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Tax expense at U.S. Statutory rate	$ 3,633,400	$ 3,719,066
State income taxes, net of Federal benefit	77,989	95,430
Research and development credits	(126,320)
Foreign-derived intangible income deduction	(540,265)	(555,256)
Other	(269,543)	(57,337)
Income tax provision	$ 2,775,261	$ 3,201,903

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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