Ingrid Daubechies/A. Grossmann/Yves Meyer: Painless non-orthogonal
expansions. J. Math. Phys. 27 (1986), 1271-1283.

Hans Georg Feichtinger/K. Gro''chenig: Non-orthogonal wavelet and Gabor
expansions, and group representations. In Beylkin a.o. 1992, ...

C. Heil/D. Waltnut: Continuous and discrete wavelet transforms.
SIAM Rev. 31 (1989), 628-666.