chapter-url: URL of an individual chapter of online source. Should be at the same site as url, if any. If chapter-url is used, url should only be used if the beginning of the work and the cited chapter are on separate webpages at the site. chapter may be wikilinked or chapter-url used, but not both. Aliases: chapterurl, contribution-url, section-url.
chapter-format: Format of the work referred to by chapter-url; for example: PDF, DOC, or XLS; displayed in parentheses after chapter. HTML is implied and should not be specified. Does not change the external link icon. Note: External link icons do not include alt text; thus, they do not add format information for the visually impaired.