a CSL style (for text format only). See get_styles
for options. Default: apa. If there's a style that CrossRef doesn't support you'll get a
(500) Internal Server Error
locale
Language locale. See ?Sys.getlocale
.progress
Show a plyr-style progress bar? Options are "none", "text",
"tk", "win", and "time". See create_progress_bar for details
of each. Only used when passing in multiple ids (e.g.
See http://www.crosscite.org/cn/ for more info on the
Crossref Content Negotiation API service.
This function is now deprecated. It will be removed in the next version
of this package. Use cr_cn instead.