Hi @Garant,
The journal_article element is the container for each article. It has an attribute that can be used to specify the article language – for example, language="en". Only one language can be specified. Within the title element, no language can be specified; I’d assume this means the journal_article's language is implied.
For the original_language_title element, a language attribute can be specified – but this is only suggested for use when the work is a translation, which I don’t think is the case in your examples.
See e.g. here for more information: http://www.crossref.org/help/schema_doc/4.3.3/4_3_3.html#original_language_title
Regards,
Alec Smecher
Public Knowledge Project Team