Volume of the journal in which a related article exists
The @vol attribute is used, along with the @, @issue, and @page attributes, to provide the metadata for the related article.
It is best practice to limit the scope of this attribute to the current journal, i.e., the one in which the current article also resides.
|Text, numbers, or special characters||The journal volume number for a related article, for example, “3” for the third volume, “125” for the one hundred and twenty-fifth, or “XV” for the fifteenth|
|Restriction: This attribute may be specified if the element is used.|