Condensed Statements of Cash Flows (USD $)	6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012
Cash flows from operating activities
Royalties received	$ 7,343,708	$ 10,024,088
Interest received	773	700
Expenses paid	(480,402)	(521,347)
Net cash provided by operating activities	6,864,079	9,503,441
Cash flows from investing activities
Maturities of U.S. Government securities	83,000	35,000
Sales of U.S. Government securities	100,012
Purchases of U.S. Government securities	(82,380)	(105,085)
Net cash provided by (used for) investing activities	100,632	(70,085)
Cash flows used for financing activities
Distributions to Unitholders	(7,478,406)	(10,824,009)
Net change in cash and cash equivalents	(513,695)	(1,390,653)
Cash and cash equivalents, beginning of year	6,727,461	10,253,474
Cash and cash equivalents, end of period	6,213,766	8,862,821
Reconciliation of net income to net cash provided by operating activities
Net income	9,827,169	14,243,178
Increase in accrued income receivable	(3,019,041)	(4,728,882)
Decrease in prepaid expenses	38,852	37,838
Increase (decrease) in accrued expenses	17,099	(48,693)
Net cash provided by operating activities	6,864,079	9,503,441
Non Cash Financing Activity
Distributions declared	$ 6,035,205	$ 8,396,806