doi_brokendate: Date the DOI is broken; use the same format as other dates in the article.
isbn: International Standard Book Number such as 978-0812695939; see Wikipedia:ISBN and ISBN. Dashes in the ISBN are optional, but preferred. Use the 13-digit ISBN where possible; this can normally be found beneath the barcode as a number beginning 978 or 979. For sources with the older 9 digit SBN system, prefix the number with a zero; thus SBN 812695-93-3 should be entered as |isbn=0812695-93-3.