Missing abstracts in most formats

[biertz]

Hey everyone,

I noticed that most output formats wouldn't provide an abstract when some do.

For example Bibtex returns without an abstract: curl -LH 'Accept: application/x-bibtex' https://doi.org/10.1159/000535565

But the csl+json formatting of the same article would return also an abstract: curl -LH 'Accept: application/vnd.citationstyles.csl+json' https://doi.org/10.1159/000535565.

Is this a bug in the formatting?