Polynomial invariants and Bell inequalities as entanglement measure of   4-qubit states
  We compare the polynomial invariants for four qubits introduced by Luque and Thibon, PRA {\bf 67}, 042303 (2003), with optimized Bell inequalities and a combination of two qubit concurrences. It is shown for various parameter dependent states from different SLOCC classes that it is possible to measure a genuine 4-qubit entanglement with these polynomials. 
Jochen Endrejat, Helmut Buettner