Statements of Cash Flows - USD ($)	6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Operating activities
Royalties received	$ 15,025,100	$ 16,056,417
Interest received	137,704	51,515
Expenses paid	(1,315,916)	(735,803)
Net cash from operating activities	13,846,888	15,372,129
Investing activities
Maturities of U.S. Government securities	32,122,312	24,168,903
Purchases of U.S. Government securities	(16,484,759)	(18,273,425)
Net cash from investing activities	15,637,553	5,895,478
Financing activity
Distributions to unitholders	(29,913,623)	(21,385,616)
Net change in cash and cash equivalents	(429,182)	(118,009)
Cash and cash equivalents, beginning of period	881,810	314,835
Cash and cash equivalents, end of period	452,628	196,826
Reconciliation of net income to net cash from operating activities
Net income	18,821,975	25,187,303
Increase in accrued income receivable	(1,481,571)	(6,820,424)
Increase in contract asset	(3,166,721)	(2,907,643)
Increase in prepaid expense	(116,226)	(97,625)
Increase (decrease) in accrued expenses	(210,569)	10,518
Net cash from operating activities	13,846,888	15,372,129
Non cash financing activity
Distributions declared and payable	$ 2,755,202	$ 2,886,402