Answered By: Steve Kuehler Last Updated: Mar 25, 2016 Views: 101
If the sources which you're citing have DOIs, they should be given in the original published source. You'll need to look up each source in print or online to find its DOI. You might not find a DOI for every source.
Cross Ref retrieves DOIs at http://www.crossref.org/SimpleTextQuery. Individual researchers can set up a free account. CrossRef provides DOIs for journal articles, books, and chapters. The user simply cuts and pastes his/her reference list into a search box, and CrossRef supplies the DOIs.