Japan, Worked Out. is built from the articles below — this site’s own reporting, written at the same desk, not an outside authority. The book does not quote them. It works from what they establish and shows its reasoning on the page, so the place to check it is here.
Where a claim rests on something other than this reporting — a government rule, a carrier’s published terms, an official advisory — the book names that source in the line itself rather than leaving you to guess.
Last checked means someone re-read the article against its sources on that date. Most pages carry only a publication date, and that is the honest state: it is not a claim that nothing has changed since.