Nice to see that the latest ICAO documents are being used.
International Civil Aviation Organisation, Air Traffic Services Planning Manual, 1st Edition, 1984
International Civil Aviation Organisation, Global Air Traffic Management Operational Concept, 1st Edition, 2005
[and yes, these are the most recent ICAO documents]
Planning for the future when one of the documents is 37 years old. And that document probably took 3-5 years to be published. Everyone who worked on that document are either long retired to at least planning retirement. Back to the future.