@@ -14,6 +14,13 @@ $endif$
1414$if(journal.pmc)$
1515<journal-id journal-id-type="pmc">$journal.pmc$</journal-id>
1616$endif$
17+$-- Fallback: an empty journal-id in case none is available.
18+$if(journal.publisher-id)$
19+$elseif(journal.nlm-ta)$
20+$elseif(journal.pmc)$
21+$else$
22+<journal-id></journal-id>
23+$endif$
1724<journal-title-group>
1825$if(journal.title)$
1926<journal-title>$journal.title$</journal-title>
@@ -28,6 +35,12 @@ $endif$
2835$if(journal.eissn)$
2936<issn pub-type="epub">$journal.eissn$</issn>
3037$endif$
38+$-- At least one issn element is required; use empty issn as fallback
39+$if(journal.pissn)$
40+$elseif(journal.eissn)$
41+$else$
42+<issn></issn>
43+$endif$
3144<publisher>
3245<publisher-name>$journal.publisher-name$</publisher-name>
3346$if(journal.publisher-loc)$