Mahtab Hoseininia Farzad Didehvar Mir Mehdi Seyyed Esfahani Inventory competition in a multi channel distribution system: The Nash and Stackelberg game http://arxiv.org/abs/0906.0151 2009 CoRR abs/0906.0151 db/journals/corr/corr0906.html#abs-0906-0151 informal publication