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Biology

Designed for biology students, this guide takes you through the Library’s resources to improve your research.

About PURLs and DOIs

Persistent URLs and DOIs

PURLs

A permanent link or a persistent URL is a URL that links to a specific record within a database. Permanent links give a specific web address to each item record, allowing records to be bookmarked by searchers, emailed to librarians for help, or linked to from other websites. 

Use permanent links in place of the URL from your browser's address bar. The browser bar address is usually a "session" URL that will expire after a short amount of time. Permanent links do not expire. Use permanent links to access journal articles, eBooks, and other digital resources again at a later time or in your works cited/references/bibliography.

DOIs

A DOI is a Digital Object Identifier—a permanent identifier that will take you straight to a document no matter where it’s located on the Internet. When available they are usually part of the citation or on the main or first page of an article.

Before you begin looking for a DOI for your article you should know: 

  1. Not all articles have a DOI number.
    • While the majority of articles published today do have DOI numbers, most older articles -more than two years old-- do not. Some publishers are adding DOIs to older articles. 
  2. While some library databases provide the DOI number as part of the article's citation, this is not consistent across databases. 
    • When you have a DOI number you can use a DOI locator to link you to the article (sometimes in full text or sometimes just the citation.)
    • DOI Locators:
  3. Here are some basic guidelines from APA Publication Manual (6th edition) for citing electronic sources.
    • For print or electronic journals, include the issue number only when the journal is paginated separately by issue.
    • The retrieval date and database information are not needed for articles retrieved from online sources. Instead, include the article's DOI.
    • If there is no DOI, provide the URL for the journal homepage as the second choice. The retrieval date is not required in this type of reference.
    • In the rare instances that the journal does not have its own homepage (such as for older journals no longer in print but converted to online documents), provide (a) the database homepage or (b) the name of the database and the accession number.
    • A retrieval date is only needed in the reference list for nonjournal instances where material might change at a later date.
    • For online newspaper and magazine articles you need not provide the specific page number, retrieval date, or exact article URL. You would provide only the periodical's home page.

(Thank you to the librarians at Nelson Memorial Library at SAGU from which I borrowed for this information.)