Strategy for investments from Zipf law(s)
  We have applied the Zipf method to extract the $\zeta'$ exponent for seven financial indices (DAX, FTSE; DJIA, NASDAQ, S&P500; Hang-Seng and Nikkei 225), after having translated the signals into a text based on two letters. We follow considerations based on the signal Hurst exponent and the notion of a time dependent Zipf law and exponent in order to implement two simple investment strategies for such indices. We show the time dependence of the returns. 
M. Ausloos and Ph. Bronlet