NATURE OF BUSINESS AND ORGANIZATION (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jul. 13, 2018	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Royalty income		$ 19,125,069	$ 14,230,174	$ 25,771,739	$ 18,990,603
Interest		26,883	7,273	64,260	13,815
Total revenues		19,151,952	14,237,447	25,835,999	19,004,418
Expenses		280,497	240,493	648,696	535,539
Net income		$ 18,871,455	$ 13,996,954	$ 25,187,303	$ 18,468,879
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)		$ 1.4384	$ 1.0668	$ 1.9198	$ 1.4077
Distributions declared per unit (Note 3) (in dollars per unit)	$ 0.22	$ 0.2200	$ 0.1600	$ 0.6700	$ 0.7100
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Royalty income			$ 882,819		$ 1,993,037
Total revenues			882,819		1,993,037
Net income			$ 882,819		$ 1,993,037
Net income per unit (Note 2) (in dollars per unit)			$ 0.0673		$ 0.1519
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Royalty income			$ 13,347,355		$ 16,997,566
Interest			7,273		13,815
Total revenues			13,354,628		17,011,381
Expenses			240,493		535,539
Net income			$ 13,114,135		$ 16,475,842
Number of units outstanding			13,120,010		13,120,010
Net income per unit (Note 2) (in dollars per unit)			$ 0.9996		$ 1.2558
Distributions declared per unit (Note 3) (in dollars per unit)			$ 0.1600		$ 0.7100