crossref, doi extract

$ curl -s "http://www.crossref.org/openurl/?id=doi:10.1038/nn.2112&noredirect=true&pid=ourl_sample:sample&format=unixref"

$ for i in *.pdf;do pdftotext -q "$i" -|grep -o "\<doi:.*"|head -n1|sed 's/doi: /doi:/;s/doi:/http:\/\/dx.doi.org\//'|awk '{print $1}'|sed 's/\.$//';done