Dual subspace nonnegative matrix factorization for person-invariant facial expression recognition. - Yi-Han Tu; Chiou-Ting Hsu (ICPR, 2012)

Dual Subspace Nonnegative Graph Embedding for Identity-Independent Expression Recognition. - Hsin-Wen Kung; Yi-Han Tu; Chiou-Ting Hsu (IEEE Trans. Inf. Forensics Secur., 2015)