@Article{Riv77a,
  author = 	 { Ronald L. Rivest },
  title = 	 { The game of {``$N$ questions''} on a tree },
  journal = 	 { Discrete Mathematics },
  OPTyear = 	 { 1977 },
  OPTmonth = 	 { February },
  date =         { 1977-02 },                  
  volume = 	 { 17 },
  number = 	 { 2 },
  pages = 	 { 181--186 },
  doi =          { 10.1016/0012-365X(77)90149-2 },
  abstract =     {
                   We consider the minimax number of questions required to
                   determine which leaf in a finite binary tree $T$ your
                   opponent has chosen, where each question may ask if the leaf
                   is in a specified subtree of $T$.  The requisite number of
                   questions is shown to be approximately the lagorithm (base~$\phi$)
                   of the number of leaves in $T$ as $T$ becomes large, where
                   $\phi=1.61803\ldots$ is the ``golden ratio''.  Specifically,
                   $q$ questions are sufficient to reduce the number of possibilities
                   by a factor of $2/F_{q+3}$ (where $F_i$ is the $i$th Fibonacci
                   number), and this is the best possible.             
                 },
}