Some bibliographic reference lists are unnumbered, some are bulleted lists, some have a counting number before each reference, and some have special symbols or author-descriptive labels (such as [Piez 2009]) constructed according to “Harvard rules” or other semantic numbering system. The first decision a publisher or archive needs to make is whether to capture such numbers using <label> or whether all such designators are generated for display or print. A repository archive may choose to preserve all numbers, a publisher may choose to generate them.
Assuming numbers will be preserved, the next decision concerns punctuation and spacing. It is possible to preserve all punctuation and spacing “3. ” or “[Lapeyre-Usdin 2009]” or to preserve just the significant portion of the label (the numeral, or the name-year) and not preserve the spacing: “3” or “Lapeyre-Usdin 2009”. The following samples, preserve the punctuation and spacing:
... <ref> <label>13.</label> <element-citation publication-type="journal" publication-format="print"> <collab>American College of Dentists, Board of Regents</collab> <article-title>The ethics of quackery and fraud in dentistry: a position paper</article-title> <source>J Am Coll Dent</source> <year>2003</year> <volume>70</volume> <issue>3</issue> <fpage>6</fpage> <lpage>8</lpage> </element-citation> </ref> ... ... <ref> <label>13.</label> <mixed-citation publication-type="journal" publication-format="print"> <collab>American College of Dentists, Board of Regents</collab>. <article-title>The ethics of quackery and fraud in dentistry: a position paper</article-title>. <source>J Am Coll Dent</source>. <year>2003</year>; <volume>70</volume>(<issue>3</issue>): <fpage>6</fpage>-<lpage>8</lpage>.</mixed-citation> </ref> ...
Usually the label applies to the reference (<ref>). Citations (<element-citation> or <mixed-citation>) are typically only numbered when multiple citations occur within a single reference. In such cases, the reference is typically numbered in series with the other, single references, and the citations are numbered using a different numbering scheme. For example, a reference numbered <label>4.</label> could have citations inside it labeled “a.”, “b.”, “c.” or “[Gaylord 2005]”. “[Beck 2006]”, “[Usdin 2009]”.