Pardalos, Panos M.; Vavasis, Stephen A. Quadratic programming with one negative eigenvalue is (strongly) NP-hard. Journal of Global Optimization. 1991, 1 (1): 15–22. S2CID 12602885. doi:10.1007/bf00120662.
Pardalos, Panos M.; Vavasis, Stephen A. Quadratic programming with one negative eigenvalue is (strongly) NP-hard. Journal of Global Optimization. 1991, 1 (1): 15–22. S2CID 12602885. doi:10.1007/bf00120662.