—Silently corrected a few typos.
—Retained publication information from the printed edition: this eBook
is public-domain in the country of publication.
—In the text versions only, text in italics is delimited by
_underscores_.
—Changed some input instructions to better fit radiobutton or checkbox
functionality.
—In the HTML version only, data entry is supported, but input is not
preserved across browser refreshes; it can be recorded by printing the
file or saving the viewer screen.