Condensed Statements of Income (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2012
Revenues
Royalty income	$ 7,834,425	$ 11,059,872	$ 10,362,842	$ 14,752,993
Interest income	290	352	680	677
Total revenues	7,834,715	11,060,224	10,363,522	14,753,670
Expenses	209,935	186,938	536,353	510,492
Net income	$ 7,624,780	$ 10,873,286	$ 9,827,169	$ 14,243,178
Number of units outstanding	13,120,010	13,120,010	13,120,010	13,120,010
Net income per unit (Note 2) (in dollars per unit)	$ 0.5812	$ 0.8288	$ 0.7490	$ 1.0856
Distributions declared per unit (Note 3) (in dollars per unit)	$ 0.4600	$ 0.6400	$ 0.5400	$ 0.7050