Condensed Statements of Cash Flows (USD $)	9 Months Ended
	Oct. 31, 2011	Oct. 31, 2010
Cash flows from operating activities
Royalties received	$ 9,006,698	$ 22,570,769
Interest received	4,597	15,513
Expenses paid	(706,064)	(649,340)
Net cash provided by operating activities	8,305,231	21,936,942
Cash flows from investing activities
Maturities of U.S. Government Securities	489,000	2,180,000
Purchases of U.S. Government Securities	(373,332)	(998,373)
Net cash provided by investing activities	115,668	1,181,627
Cash flows used for financing activities
Distributions to Unitholders	(17,056,013)	(19,352,015)
Net change in cash and cash equivalents	(8,635,114)	3,766,554
Cash and cash equivalents, beginning of year	8,693,691	8,444,697
Cash and cash equivalents, end of period	58,577	12,211,251
Reconciliation of net income to net cash provided by operating activities
Net income	26,951,882	27,190,825
Increase in accrued income receivable	(19,035,423)	(2,446,838)
Increase in prepaid expenses	(39,635)	(23,215)
Decrease in accrued expenses	(38,593)	(13,830)
Increase (Decrease) in deferred royalty revenue	467,000	(2,770,000)
Net cash provided by operating activities	8,305,231	21,936,942
Non Cash Financing Activity
Distributions declared	$ 14,694,411	$ 11,939,209