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The format description does not make much sense like it is now. Especially the part 'and assigned by the SCHAC URN Registry for this attribute at ' does not match the context.
Also updating the reference to ISO3166-2 would make sense.
How about something like this?
Format: urn:schac:homeOrganizationType:<country-code>:<string> <country-code> = int
<string> MUST be registered in the [SCHAC-URN-Registry] <country-code> = valid two-letter [ISO3166-2] country code
<string> from a nationally controlled vocabulary, published through the URI identified at the [SCHAC-URN-Registry]
Typo on page 10 in 'schacHomeOrganizationType' Examples
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