elle">67</A>]. If one assumes a local decomposition of
the phase space into directions with different stretching or contraction rates,
then the spectrum of exponents is the proper average of these local rates over
the whole invariant set, and thus consists of as many exponents as there are
space directions. The most prominent problem in time series analysis is that
the physical phase space is unknown, and that instead the spectrum is computed
in some embedding space. Thus the number of exponents depends on 