Condensed Statements of Cash Flows (USD $)	6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011
Cash flows from operating activities
Royalties received	$ 10,024,088	$ 8,807,077
Interest received	700	2,999
Expenses paid	(521,347)	(565,365)
Net cash provided by operating activities	9,503,441	8,244,711
Cash flows from investing activities
Maturities of U.S. Government securities	35,000	332,000
Purchases of U.S. Government securities	(105,085)	(217,098)
Net cash provided by (used for) investing activities	(70,085)	114,902
Cash flows used for financing activities
Distributions to Unitholders	(10,824,009)	(9,184,007)
Net change in cash and cash equivalents	(1,390,653)	(824,394)
Cash and cash equivalents, beginning of year	10,253,474	8,693,691
Cash and cash equivalents, end of period	8,862,821	7,869,297
Reconciliation of net income to net cash provided by operating activities
Net income	14,243,178	13,195,545
Increase in accrued income receivable	(4,728,882)	(5,792,237)
Decrease (increase) in prepaid expenses	37,838	(93,676)
Decrease in accrued expenses	(48,693)	(55,921)
Increase in deferred royalty revenue		991,000
Net cash provided by operating activities	9,503,441	8,244,711
Non Cash Financing Activity
Distributions declared	$ 8,396,806	$ 7,872,006