Effective algorithm for solving a two-level facility location problem on a tree-like network

A two-level facility location problem on a tree-like network is considered. The transportation cost between each pair of sites is defined as the length of the corresponding path in the network. An exact algorithm for solving the problem with time-complexity equals to $O(nm^3)$ is constructed, where $n$ is the number of consumers and $m$ is the maximum number of facilities at both levels. Il. 3, bibliogr. 7.