Condensed Statements of Income (USD $)	3 Months Ended		9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Revenues
Royalty income	$ 6,347,390	$ 11,814,026	$ 16,710,231	$ 26,567,019
Interest income	238	394	918	1,071
Total revenues	6,347,628	11,814,420	16,711,149	26,568,090
Expenses	211,113	190,394	747,465	700,887
Net income	$ 6,136,515	$ 11,624,026	$ 15,963,684	$ 25,867,203
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)	$ 0.4677	$ 0.8860	$ 1.2167	$ 1.9716
Distributions declared per unit (Note 3) (in dollars per unit)	$ 0.5100	$ 1.1300	$ 1.0500	$ 1.8350