@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.}
}