We consider special cases of a modified version of the Tower of Hanoi puzzle and demonstrate how to find upper bounds on the minimum number of moves that it takes to complete these cases.
 Gregg, S.B., Orozco, J. “The Broncho Tower a modification of the Tower of Hanoi puzzle”, Rose-Hulman Undergrad. Math. J., 4, no. 2, 47-58, 2013.
 “The Tower of Stanford”, Problems and Solutions, American Mathematical Monthly, 111, no. 4, 364-365, April 2004.