As I am working on designing new travel documents, I updated my library to the eighth edition of the ICAO9303 series [1]. These books define what a travel document (passport, identity card, visa) MUST contain and what is optional. It’s interesting to compare what changes here over the many years of this open standard. 1/n
[1] https://www.icao.int/publications/pages/publication.aspx?docnum=9303