Note 3 - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended	6 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income	$ 664,538	$ 410,753	$ 1,543,971	$ 803,130
Weighted average common shares outstanding - basic (in shares)	3,209,046	3,188,895	3,209,046	3,188,895
Weighted average common shares outstanding - diluted (in shares)	3,214,841	3,196,516	3,214,841	3,196,516
Income per common share - basic and diluted (in dollars per share)	$ 0.21	$ 0.13	$ 0.48	$ 0.25
Anti-dilutive shares (in shares)	174,465	124,169	174,465	124,169

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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