Second-order necessary and sufficient conditions in nonsmooth optimization. - L. R. Huang; K. F. Ng (Math. Program., 1994)

On Lower Bounds of the Second-Order Directional Derivatives of Ben-Tal, Zowe, and Chaney. - L. R. Huang; K. F. Ng (Math. Oper. Res., 1997)

On Minimizing and Critical Sequences in Nonsmooth Optimization. - L. R. Huang; K. F. Ng; J. P. Penot (SIAM J. Optim., 2000)

On First- and Second-Order Conditions for Error Bounds. - L. R. Huang; K. F. Ng (SIAM J. Optim., 2004)