  Computing equilibria of games is a central task in computer science. A large
number of results are known for \emph{Nash equilibrium} (NE). However, these
can be adopted only when coalitions are not an issue. When instead agents can
form coalitions, NE is inadequate and an appropriate solution concept is
\emph{strong Nash equilibrium} (SNE). Few computational results are known about
SNE. In this paper, we first study the problem of verifying whether a strategy
profile is an SNE, showing that the problem is in $\mathcal{P}$. We then design
a spatial branch--and--bound algorithm to find an SNE, and we experimentally
evaluate the algorithm.
