These are in no particular order!

• dissertation (zipped postscript)
  by J. Rice, title "Autocorrelation Coefficients in the Classification and Representation of Switching Functions"
  
  
• Methods for Calculating Autocorrelation Coefficients (postscript)
  by J. Rice and J. C. Muzio, presented at IWSBP2000.
  
  
• details on the disjoint method referred to in the above paper (postscript)