Condensed Statements of Cash Flows - USD ($)	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016
Operating activities
Royalties received	$ 24,271,530	$ 3,910,855
Interest received	39,896	3,819
Expenses paid	(825,270)	(953,926)
Net cash from operating activities	23,486,156	2,960,748
Investing activities
Maturities of U.S. Government securities	9,933,171	5,690,347
Purchases of U.S. Government securities	(35,768,880)
Net cash (used for) from investing activities	(25,835,709)	5,690,347
Financing activity
Distributions to unitholders	(11,152,009)	(5,904,005)
Net change in cash and cash equivalents	(13,501,562)	2,747,090
Cash and cash equivalents, beginning of year	13,695,168	2,587,165
Cash and cash equivalents, end of period	193,606	5,334,255
Reconciliation of net income to net cash from operating activities
Net income	28,440,087	5,198,145
Increase in accrued income receivable	(2,792,115)	(2,078,052)
Increase in prepaid expense	(41,078)	(36,841)
Decrease in accrued expenses	(21,323)	(122,504)
Decrease in deferred royalty revenue	(2,099,415)
Net cash from operating activities	23,486,156	2,960,748
Non cash financing activity
Distributions declared and payable	$ 8,396,806	$ 1,312,001