GIPS: measure of dispersion

[singlesong80]

Anyone knows the difference between internal measure of dispersion and external one?
External one is in the recommended disclosure, how about the internal one?

 

[elcfa]

I find this in the CFAI text as foot note on the example.
“Internal dispersion is calculated using the equal weighted standard deviation of all portfolios that were included in the composite for the entire year.”
Cannot find anything about external dispersion. Where did you find it?

 

[McLeod81]

Internal Dispersion:
Dispersion of accounts returns WITHIN the composite (shows how similar the accounts are). Example: Standard deviation of composite account returns over one month.
External Dispersion:
Dispersion of composite returns over a certain time period. Example: Standard deviation of overall composite returns over 5 years.