Only tables are transcribed; the running text, photographs, maps and diagrams are not. Every text page was read; this edition has no statistical appendix. Printed totals that do not add up are kept as printed and noted; every such table was transcribed a second time independently, and disputed cells went to a third reader (agreement settles a cell; otherwise it is marked unreadable). The one-sentence context notes are written by the transcriber from the surrounding text.