Statements of Cash Flows - USD ($)	9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Operating activities
Royalties received	$ 10,724,507	$ 27,121,064
Interest received	38,297	176,140
Expenses paid	(1,683,487)	(1,695,941)
Net cash from operating activities	9,079,317	25,601,263
Investing activities
Maturities of U.S. Government securities	55,381,743	37,034,247
Sales of U.S. Government securities	236,992
Purchases of U.S. Government securities	(51,574,900)	(30,473,442)
Net cash from investing activities	4,043,835	6,560,805
Financing activity
Distributions to unitholders	(17,187,214)	(32,668,825)
Net change in cash and cash equivalents	(4,064,062)	(506,757)
Cash and cash equivalents, beginning of period	10,177,655	881,810
Cash and cash equivalents, end of period	6,113,593	375,053
Reconciliation of net income to net cash from operating activities
Net income	13,414,023	24,972,171
Increase in accrued income receivable	(1,113,742)	(69,219)
Increase in contract asset	(736,137)	56,357
Increase in prepaid expense	(91,217)	(61,816)
Increase (decrease) in accrued expenses	118,110	(234,359)
Decrease in contract liability	(2,511,720)	938,129
Net cash from operating activities	9,079,317	25,601,263
Non cash financing activity
Distributions declared and payable	$ 4,723,204	$ 11,414,408