Classifying N-qubit Entanglement via Bell's Inequalities
  All the states of N qubits can be classified into N-1 entanglement classes from 2-entangled to N-entangled (fully entangled) states. Each class of entangled states is characterized by an entanglement index that depends on the partition of N. The larger the entanglement index of an state, the more entangled or the less separable is the state in the sense that a larger maximal violation of Bell's inequality is attainable for this class of state. 
Sixia Yu, Zeng-Bing Chen, Jian-Wei Pan, and Yong-De Zhang