The latest version of the Radio Regulations is the 2016 edition, contained in the Volume 1 - 4 red books. A review of the Radio Regulations has taken place by the World Radiocommunication Conference 2015 (WRC-15).
Table of Contents of the Radio Regulations
|Volume 1||The Articles|
|Volume 2||The Appendices|
|Volume 3||The Resolutions and Recommendations|
|Volume 4||ITU-R Recommendations incorporated by reference|
The body of the text is divided in to Chapters, Articles and Provisions; then come the Appendices, lastly the Resolutions - RES and Recommendations - REC. The official way of referring to a provision is "The provisions of No. 9.21 " and to an appendix "Appendix 4 of the Radio Regulations", and it is this formulation which should be used in official documents. However, one often sees "No. 9.21" and "AP 4" for short.