Condensed Statements of Cash Flows (USD $)	6 Months Ended
	Jul. 31, 2011	Jul. 31, 2010
Cash flows from operating activities
Royalties received	$ 8,807,077	$ 10,361,187
Interest received	2,999	11,175
Expenses paid	(565,365)	(428,048)
Net cash provided by operating activities	8,244,711	9,944,314
Cash flows from investing activities
Maturities of U.S. Government Securities	332,000	1,540,000
Purchases of U.S. Government Securities	(217,098)	(998,861)
Net cash provided by investing activities	114,902	541,139
Cash flows used for financing activities
Distributions to Unitholders	(9,184,007)	(8,856,007)
Net change in cash and cash equivalents	(824,394)	1,629,446
Cash and cash equivalents, beginning of year	8,693,691	8,444,697
Cash and cash equivalents, end of period	7,869,297	10,074,143
Reconciliation of net income to net cash provided by operating activities
Net income	13,195,545	15,794,259
Increase in accrued income receivable	(5,792,237)	(3,084,445)
Decrease (increase) in prepaid expenses	(93,676)	14,389
Decrease in accrued expenses	(55,921)	(9,889)
(Decrease) Increase in deferred royalty revenue	991,000	(2,770,000)
Net cash provided by operating activities	8,244,711	9,944,314
Non Cash Financing Activity
Distributions declared	$ 7,872,006	$ 10,496,008