<journal-subtitle>

Appears in	Frequency
<journal-title-group>	Zero or One time

Contains the subtitle of the journal.

Example:

...
<journal-meta>
    ...
    <journal-title-group>
        <journal-title>Meta</journal-title>
        <journal-subtitle>Journal des Traducteurs</journal-subtitle>
        ...
    </journal-title-group>
    ...
</journal-meta>
...