Statements of Income (Unaudited) - USD ($)	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Revenue
Revenue	$ 6,294,696	$ 7,107,906
Cost of sales	1,092,037	1,396,005
Gross profit	5,202,659	5,711,901
Expenses
Research and development	973,067	989,026
Selling, general, and administrative	330,009	328,761
Total expenses	1,303,076	1,317,787
Income from operations	3,899,583	4,394,114
Interest income	459,039	424,770
Income before taxes	4,358,622	4,818,884
Provision for income taxes	751,203	873,835
Net income	$ 3,607,419	$ 3,945,049
Net income per share – basic (in dollars per share)	$ 0.74	$ 0.81
Net income per share – diluted (in dollars per share)	0.74	0.81
Cash dividends declared per common share (in dollars per share)	$ 1	$ 1
Weighted average shares outstanding
Basic (in shares)	4,846,010	4,842,010
Diluted (in shares)	4,850,388	4,850,479
Product [Member]
Revenue
Revenue	$ 6,085,364	$ 6,870,646
Contract Research and Development [Member]
Revenue
Revenue	$ 209,332	$ 237,260