These functions are gone, no longer available.
cr_citation(): Crossref is trying to sunset their
OpenURL API, which this function uses. So this function is now removed.
See the function cr_cn(), which does the same things, but with
more functionality, using the new Crossref API.
pmid2doi() and doi2pmid(): The API behind
these functions is down for good, see id_converter() for
similar functionality.
cr_search(): The functionality of this function can
be achieved with the new Crossref API. See functions cr_works()
et al.
cr_search_free(): The functionality of this function can
be achieved with the new Crossref API. See functions cr_works()
et al.
crosscite(): The functionality of this function can be
achieved with cr_cn()
cr_fundref(): Crossref changed their name "fundref"
to "funders", so we've changed our function, see cr_funders()
cr_ft_text(): This function and other text mining
functions are incorporated in a new package crminer.
cr_ft_links(): This function and other text mining
functions are incorporated in a new package crminer.
cr_ft_pdf(): This function and other text mining
functions are incorporated in a new package crminer.
cr_ft_plain(): This function and other text mining
functions are incorporated in a new package crminer.
cr_ft_text(): This function and other text mining
functions are incorporated in a new package crminer.
cr_ft_xml(): This function and other text mining
functions are incorporated in a new package crminer.
as.tdmurl(): This function and other text mining
functions are incorporated in a new package crminer.
extract_xpdf(): This function and other text mining
functions are incorporated in a new package crminer.