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Dragonfly, Summer 2001

Citing the Internet: A Brief Tour

Susan Barnes
Resource Sharing Coordinator

The National Library of Medicine has issued its official Recommended Formats to use when citing Internet resources. These are formats that NLM uses, and recommends we all use, for references to any sort of electronic publication - ebook, ejournal, ejournal article, homepage on the Web, entry from a listserv, etc. - in a bibliography or footnote. Many of you will want to bookmark this new publication. It is rich with information and examples and is likely to become an indispensable supplement to NLM's recommended formats for citing physical publications such as printed books or journal articles.

This new resource has been published on the Internet, and here is the citation for it in its own recommended format:

Patrias, Karen. National Library of Medicine recommended formats for bibliographic citation. Supplement: Internet formats [Internet]. Bethesda (MD): National Library of Medicine; 2001 Jul [cited 2001 Aug 8]. 106p. Available from:

You'll notice that this looks quite similar to a citation to a book. In fact, the general guideline for Internet resources is to follow basic rules for citing. Look for an author (or some responsible entity), a title, a place of "publication" and publisher, a date of publication, and "pagination" (length). In addition, a citation to an Internet resource needs an availability statement that presents the network address. After all, one purpose of citing a document is to make it possible to find a copy! NLM also recommends the inclusion in brackets of a medium designator, [Internet], after the title, to make it clear that the item being cited is virtual, not physical. If you wish, you can include a brief note at the end of the citation to indicate restrictions or requirements for viewing an item.

Of course, there is a lot of variability in how Internet resources are presented, so it can be difficult or impossible to find some standard citation information.

If there is no clear author, do not use "anonymous." Instead, list the resource under title.

If there is no clear title, look for:

The place of "publication" is where the sponsor of the resource is located, and if that cannot be found use [place unknown].

Dates are extremely important since the electronic environment is so volatile. Include the date of publication plus date of revision, if one or both can be found. Always include date of citation, i.e. when you viewed, downloaded, or printed the resource. If no date of publication or revision is present, a date of citation at least places the document somewhere in time. Date information will help future readers decide whether they need to read the item, and can be invaluable in helping to find a copy of it. NLM recommends that we use a year-month-day format for dates, e.g. 2001 Aug 10.

Pagination is often absent in the electronic milieu, but you may wish to indicate in brackets an estimate of the item's size or the number of screens it takes up. This helps the reader know what to expect.

URLs in availability statements should never end with a period unless the URL itself ends with a slash. For example::

Although this may seem a trivial point, it can make a big difference when cutting and pasting a URL or using it to link directly.

Otherwise, NLM's recommendations allow you to make choices in whether to use authors' full names or initials, whether to include author addresses, whether to spell out journal titles or use NLM abbreviations, whether to include 2-letter state or country abbreviations, and whether to combine content designators with medium designators, e.g. [bibliography on the Internet] or [database on the Internet]. Whatever you decide, use consistency throughout your list of references.

When deciding how to cite an Internet resource, think of your readers, and ask yourself what information they'll need for evaluating, finding, and using the item. Think also about the resource itself. Is it a one-time publication, like a book? Is it published at regular intervals over time, like a journal? Is it a section of a publication, like a book chapter, journal article, chart, or graphic? NLM's recommendations are organized by type of resource, by publication pattern, and by whether a whole item or just part of one is being cited. A few basic examples are presented below, but remember that this is just a glimpse into the wealth of information provided in the full set of recommendations.

If you are creating a citation for a type of Internet resource that is not represented in this brief tour, consult the complete work. In addition, the recommendations' author, Karen Patrias, would be happy to discuss questions on correct format, and she plans to update this publication when new types of Internet documents emerge. Karen - who can be reached at (301) 435-4887 or - is not only the author of these Recommended Formats for citing the Internet but also wrote the original volume to which this is a supplement:

Patrias, Karen. National Library of Medicine recommended formats for bibliographic citation. Bethesda (MD): The Library; 1991 Apr. Available from: NTIS, Springfield, VA; PB91-182030.

FINAL NOTE: If you have difficulty opening the new recommended formats for citing Internet resources, you may need to adjust your Acrobat Reader preferences. Karen Patrias provided information on how to do that in a MEDLIB-L posting:

Patrias, Karen. Accessing "Citing the Internet." In: MEDLIB-L [Internet]. (Chicago, IL): Medical Library Association; 2001 Aug 2, 15:45:57 [cited 2001 Aug 13]. Available from:

Selected examples of citing the Internet:

Articles in Journals or Other Periodicals:

Tong, Vincent; Abbott, Frank S.; Mbofana, Salome; Walker, Michael J. In vitro investigation of the hepatic extraction of RSD1070, a novel antiarrhythmic compound. Journal of Pharmacy & Pharmaceutical Sciences [Internet]. 2001 [cited 2001 May 3]; 4(1):15-23. Available from:
Connolly C. Deaths from heart disease, cancer, AIDS declined in '99. The Washington Post Online [Internet]. 2001 Jun 27 [cited 2001 Jun 28]:A03. [about 31 paragraphs]. Available from:


Lawrence, Ruth A. A review of the medical benefits and contraindications to breastfeeding in the United States [Internet]. Arlington (VA): National Center for Education in Maternal and Child Health; 1997 Oct [cited 2000 Apr 24]. 40 p. Available from: Hardin meta directory of Internet health resources [Internet]. Iowa City (IA): University of Iowa, Hardin Library for the Health Sciences; [updated 2001 Apr25; cited 2001 Apr 30]. Available from:

Chapters in Books:

Monath, Thomas P. Dengue: the risk to developed and developing countries. In: Roizman, Bernard, editor. Infectious diseases in an age of change: the impact of human ecology and behavior on disease transmission [Internet]. Washington: National Academy Press; 1995 [modified 2001 Mar 2; cited 2000 Apr 4]. P. 43-58. Available from:
Dobzhansky, Theodosius; Robinson, Arthur. The physical basis of heredity. In: Encyclopedia Britannica [Internet]. Chicago: Inc.; c1999-2000 [cited 2000 Mar 17]. [about 22 paragraphs]. Available from:,5716,120933+1+111157,00.html


Prevention News Update Database [Internet]. Rockville (MD): Centers for Disease Control and Prevention (US), National Prevention Information Network. 1988 Jun - [cited 2001 Apr 12]. Available from:
Pulse Generator Database [Internet]. Irvington (NY): Amadeus Multimedia Technology, Inc.; c1995-98 - [updated 2000 Sep 19; cited 2001 Jun 23]. Available from: Searchable by manufacturer, model, and x-ray code.


The Urbana atlas of pathology [Internet]. Urbana (IL): University of Illinois College of Medicine at Urbana-Champaign; c1994-97 [modified 1997 Nov 4; cited 2001 Apr 24]. Image No. 034, Left ventricular hypertrophy, heart; [about 1 screen]. Available from:
Zhuomei L, Joseph D, Bugnard E, Zaal KJ, Ralson E. Golgi complex reorganization during muscle differentiation: visualization in living cells and mechanism. Mol Biol Cell [Internet]. 2001 Apr [cited 2001 Jun 23]; 12(4):795-808. Figure 2, Golgi complex dynamics in C2 myoblasts and during fusion [video]; [about 30 sec.] Available from: System Requirements: RealPlayer Basic or Quicktime Player required to view.


Digital Journal of Ophthalmology [Internet]. Boston: Harvard Medical School, Massachusetts Eye and Ear Infirmary. Vol. 1, No. 1, 1997- [cited 2001 Apr 1]. Available from:
The Online Journal of Current Clinical Trials [Internet]. New York: Chapman & Hall. Doc. No. 1, 1992 - Doc. No. 200-2001, 1996 [cited 2001 May 3]. Available from: Subscription required.

Sections of Web Sites and Databases:

Inhalant abuse [Internet]. Bethesda (MD): National Institute on Drug Abuse (US); 1994 [revised 2000 Jul; cited 2001 Mar 1]. How can inhalant abuse be recognized; p. 5. (NIH pub. No.; 00-3818). Available from: System Requirements: Adobe Acrobat.
CancerNet [Internet]. Bethesda (MD): National Cancer Institute (US); [modified 2001 May; cited 2001 May 10]. Ovarian epithelial cancer (PDQ): treatment - patients; [about 5 p.]. Available from:

Web Sites

The AAMC's Academic Medicine Web Site [Internet]. Washington: Association of American Medical Colleges; c1995-97 [cited 1997 Nov 4]. Available from:
University of Maryland [Internet]. College Park (MD): The University; c2001 [updated 2001 Apr 28; cited 2001 May 1]. Available from:

Email, and Email Discussion Lists (aka "Listservs")
These are presented last because they are personal communications and may not be appropriate for inclusion in a reference list. Nevertheless, if you do decide to cite email messages, here is the format:

Burns, Edwin (Center for Toxicology and Environmental Health, Little Rock, AR. Availability of documents from 2,4-D study [Internet]. Message to: Margaret Brennan (Headquarters Library, Environmental Protection Agency, Washington, DC. 2001 Mar 23, 1:34pm [cited 2001 Mar 24]. [about 5 paragraphs].

Smith, John. WebMD. In: MEDLIB-L [Internet]. [Chicago (IL): Medical Library Association]; 1998 Feb 23, 10:27 am [cited 1998 Feb 24]. [about 5 paragraphs]. Available from: MEDLIB-L@LISTSERV.ACSU.BUFFALO.EDU.

Dragonfly, Summer, 2001 -- Vol.32, Number 3
(posted on PNRNews August 21, 2001)
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