: You can buy the most recent edition (currently around Edition 199) from the ICAO Store or through distributors like Accuris Standards Public Libraries and Repositories
According to ICAO Annex 15 (Aeronautical Information Services), all flight plans must use the location indicators listed in Doc 7910. If a pilot files a flight plan with an incorrect or obsolete code (e.g., using a code for a closed airport), the flight plan will be rejected by air traffic control systems worldwide. doc 7910 pdf
: Member States and governmental bodies can often access these digital publications via the ICAO Secure Portal. : You can buy the most recent edition