@article{Zukerman2001polynomially,
    author = {M. Zukerman and L. Jia and T. Neame and G. Woeginger},
    title = {A polynomially solvable special case of the unbounded knapsack problem},
    journal = {Operations Research Letters},
    volume = {29},
    number = {1},
    pages = {13-16},
    month = {Aug.},
    year = {2001},
    abstract = {We consider a special case of the unbounded knapsack problem that is characterized by a set of simple inequalities that relate item weights to item costs. We present an algorithm for this special case with time complexity linear in the number of items.}
}