1) Oppenheim "Digital Signal Processing"
2) P. Stoica, R. Moses "Spectral Analysis of signals", Upper Saddle River, New Jersey 07458
3) Prabhakar S. Naidu "Modern Spectrum Analysis of Time Series" CRC Press
4) N. Golyandina, V. Nekrutkin, A. Zhigljavsky "Analysis of Time Series Structure: SSA and Related Techniques"
5) N. Huang, Nii O. Attoh-Okine "The Hilbert-Huang Transform in Engineering"
6) N. Huang "Hilbert-Huang Transform and its Applications", World Scientific, 2005
With respect,
Dmitrij