Investments - Short term invesmtments (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Notes to Financial Statements
U.S. treasury bills	$ 4,490,954	$ 1,148,395
Commercial paper	0	499,383
Certificates of deposit	200,000	200,000
Total short-term investments	$ 4,690,954	$ 1,847,778

Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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