Need References on fast/slow alpha and beta

[N020BA at tamvm1.tamu.edu]

  I've heard that the alpha band is best divided into alpha1 and alpha2
because some people's alpha is slower that others. I've also heard that
the high end of the beta band relates to cognition and should be divided
into two bands, beta1 and beta2. Are there references for this? I will
post a summary of replies.
 
       Thank you very much!