encoding bibliographical references to numbered entries

Hello all,

Is there a standard way of encoding bibliographical entries where (instead of a page) a numbered entry or range of numbered entries is cited?

For example:

<bibl><title>Bibliotheca Hagiographia Latina>, 5625-6</bibl>

<citedRange> does not have "number" (or an equivalent) as an accepted value of @unit - is there an alternative?

Thanks

Matthew