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Library of Congress Subject Head

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Library of Congress Subject Headings Laura W. Harris Copyright 2013 


Understanding & Using 

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Dispel any dread and fear you may have had over research by following the step-by-step mapAvoid procrastination by starting to get your thoughts down as soon as you receive the assignmentCompile just the right amount of material, neither too much nor too littleUse the many tips and thinking tools to boost your efficiency


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Introduction: Why should I bother  
   to learn about LC Subject Headings?                                   1


How can LC Subject Headings help me
   be more effective and efficient in finding resources?     2


You've probably already used  LC Subject

   Headings                                                                                         4


What does the LC Subject Heading 

   system DO?                                                                                   6


How do I identify assigned LC Subject
   Headings?                                                                                       8


Table of Contents

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How do I use LC Subject Headings in searches?           17


Concluding Thoughts                                                               25


Why was the LC Subject Heading system
    created?                                                                                      26

Table of Contents (continued)

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My keyword searching works pretty well, so how is the LCSH system worth my time?


Using Library of Congress Subject Headings can help you be more effective and efficient in your research. They can help you find relevant resources that you might miss with just keyword searching.


Read on to learn how this system is organized and how to use it in searching library catalogs and many article databases. Learning the system is a real "Ah-ha!" experience for many people!

Introduction: Why should I bother to learn about LC Subject Headings?

The main Reading Room in the Library of Congress.


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How can LC Subject Headings help me be more effective and efficient in finding resources?

Here's an example:

Say you're researching climate change. You search in a library catalog or article database using this phrase in the keyword search box and find some resources but not quite what you're looking for.

If you know how to use the LC Subject Heading system, you'll find out that the assigned heading is actually "Climatic changes". So if the record of an item doesn't actually contain the specific phrase "climate change", it would not come up in your search. Instead of a keyword search, you can enter "Climatic change" in the subject box and find more items.

Furthermore, in searching specifically for assigned subject headings, you'll find additional headings such as "Greenhouse effect, Atmospheric", "Global environmental change", "Global warming", and "Environmental degradation". One of these may tie in more closely to your interests.


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How can LC Subject Headings help me be more effective and efficient in finding resources? (continued)

You'll find even more focused headings such as "Animals - Effect of global warming on", "Plants - Effect of global warming on", and "Water-supply - Effect of global warming on".

You'll also discover assigned subheadings that can be used with any of the major headings to focus your search in that direction - such as "Research", "Religious aspects", "Moral and ethical aspects", "Law and Legislation". You'll know that you can use geographic terms to limit your search to specific areas.

Are you convinced now? Then keep reading!


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You've probably already used LC Subject Headings

(1) by linking from a subject entry in a library catalog.


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(2) by linking from a subject entry in an article database that uses LC Subject Headings as the basis of its indexing (such as Academic Search Premier).

You've probably already used LC Subject Headings (continued)


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LC Subject Headings identify what a book or DVD or other item is about. The Subject Heading system is what we call a "controlled vocabulary" system. That means that highly structured, specific terms are assigned to an item to accurately describe it.

Unlike internet search engines, most library catalogs and article databases include the option to search by a "subject keyword". If you enter a term in this kind of search that is not included in the assigned LC subject headings, you may get no results or your results list may have few relevant records. This does not mean that there are few or no works about your topic; it just means that your term is not found in the LCSH system.

For example, if you search a library catalog for the general keywords "battered women," you may find enough materials to meet your immediate need. However, by not identifying assigned LC subject headings such as "Abused women," "Abused wives," and "Wife abuse", you may miss the most relevant & significant resources on your topic.

What does the LC Subject Heading system DO?


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In addition, LC Subject Headings identify types of resources such as bibliographies, encyclopedias, commentaries, dictionaries, diaries, and so forth. So, for example, they could help you find specialized reference materials such as the Encyclopedia of Bioethics. Or they can help you find primary sources on a topic, such as The Mountains We Have Crossed: Diaries and Letters of the Oregon Mission, 1838.

To summarize, some advantages of using LC Subject Headings are that they:

(1) identify specificallywhat an item is about;

(2) identify what typeof material an item is;

(3) provide more "access points" or paths to relevant

(3) make your research more effective and efficient.

What does the LC Subject Heading system do? (continued)


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There are a number of ways to identify assigned LC Subject Headings:

from the library catalog record of an itemfrom the Cataloging-in-Publication information on the verso (the back of the title page)from the record of an article in a database which uses LC subject headings in their indexingfrom the Library of Congress websitefrom the WorldCat database of library holdings around the worldfrom the "Red books" in the library.

All of these methods will be explained in the following pages.

I recommend that you start two lists when you begin your research:

A list of keywords on your topic that you come across in your reading;A list of assigned LC subject headings that you identify.


How do I identify assigned 

LC Subject Headings?


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Library catalog records include subject terms. These are usually from the Library of Congress system, even if a library uses the Dewey classification system to determine the numbers on the spine of a book.

Identifying LC Subject Headings from  Library Catalog Records

All of the terms in the "Subjects" field above are from the LC Subject Heading system. 


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Here's your trivia fact for the day: the back of the title page of a book is called the verso. In addition to information about the publisher and date of publication, the verso often  contains "Cataloging-in-Publication Data" supplied by the Library of Congress. This data includes the title, author, ISBN numbers, LC Subject Headings selected by the cataloger, and LC and Dewey classification numbers. 

Identifying LC Subject Headings from the Verso of a Book 


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Many article databases use the LC Subject Heading system as the foundation for their indexing. The EBSCOhost Academic Search Premier database of articles lists LC subject headings under "Subject Terms".

Identifying LC Subject Headings from Article Database Records


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The Library of Congress website ( includes a searchable database of subject headings and other "authorities". The Library of Congress assigns not only authorized subject headings but also the authorized version of the title and the name of the author. Librarians strive to maintain authorities so that, for example, you don't need to search for an author by various versions of his/her name or for multitudinous keywords.

To find the web page below, go to

Identifying LC Subject Headings on the Library of Congress Website


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Identifying LC Subject Headings in the WorldCat Database   

The WorldCat database includes records of holdings from all member libraries around the world. Its Advanced Search page has an icon labeled "Subjects".

If you click on this icon, you'll see a search box to search for LC Subject Headings. If I search for "indigenous peoples", I see this:


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Identifying LC Subject Headings in the WorldCat Database (continued) 

If I click on "Expand", I'll see a scope note that distinguishes this subject heading from a related one called "Ethnology". I'll also see what this heading is used instead of ("Used for") as well as "Broader Subject Headings", "Topical Sub-headings", "Geographical Sub-Headings", and a "Reference" note. These can help me broaden or narrow my focus.


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The "Red Books" are a 6-volume set of LC subject headings with extensive cross-references. Your library may have a set that you can look at. Sometimes it's easier and faster to skim pages in print than on the web.


The 2013 edition will be the last edition published in book form.


On the next page is a copy of listings for "Mental Illness".

Identifying LC Subject Headings in the "Red Books" 


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UF = Used for


BT = Broader terms


RT = Related terms


NT = Narrower terms


May Subd Geog =

     May subdivide


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When searching for items in a library catalog, LC Subject Headings can help you get into the specifics of a topic really quickly. In the catalog shown below, I selected "Subject alphabetical" from the drop down box next to "Search" and then typed "quantum theory" in the text box.

How do I use LC Subject Headings in searches?

If I selected "General Keyword" in the search box, I might get hundreds or even thousands of results -  way too many to wade through and not at all specific. However, on the next page you'll see the results of searching by subjects.


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Now I'm in the indexof all subject headings found in the records in the library catalog. In this theological library where I work, we have only a handful of titles on Quantum theory. But I can see what phrases are not assigned subject headings and scan the list of subheadingsto find more specifically what I'm seeking. The larger the library collection, the more valuable this method is.

Using the "Subject alphabetical" search is another way of identifyingsubject headings. If I'd typed in "Quantum mechanics", I'd have found that I need to use "Quantum theory" instead.

How do I use LC Subject Headings in searches? - 2


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Once I've Identified some assigned subject headings, I can do more complex searches such as the following:

After looking at the subject headings in some of the records, I find I could further focus my search by using another assigned heading such as virginity, marriage, preaching, Crusades, etc. My interest might be piqued by a focused topic I hadn't even thought of before.

I get a list of 92 results:

How do I use LC Subject Headings in searches? - 3 


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Or I can combine an assigned subject heading with a General Keyword or Title Keyword:

How do I use LC Subject Headings in searches? - 4


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How do I use LC Subject Headings in searches? - 5

But wait, there's more!  In addition to helping you focus your search more specifically on your topic, LC Subject Headings can also help you find specific types of resources. Look at the subheadings below.

Atlases                                                              Handbooks, manuals, etc. 

Bibliography                                                    Illustrations

Case studies                                                    Interviews

Chronology                                                      Manuscripts

Correspondence                                             Maps

Criticism and interpretation                         Personal narratives

Diaries                                                              Photograph collections

Dictionaries                                                     Pictorial works

Directories                                                       Statistics


These are called "floating subheadings" because they can be used with many different main subject headings. You'll notice many more of these floating subheadings as you continue your research.


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How do I use LC Subject Headings in
searches? - 6

In the WorldCat database of library holdings all over the world, I'd get a results list like the one below. 

(Use "Subject Phrase" when you know a complete phrase; use "Subject" when you just know a single subject heading keyword.)

So to find diaries of women pioneers, I could do this search:


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How do I use LC Subject Headings in searches? - 7

As was mentioned earlier, some article databases use the LC Subject Heading system as the foundation of their indexing. These include Academic Search Premier/Elite, ATLAReligion, Business Source Premier/Elite, and others. 

Sometimes the subject headings are called "Descriptors" in a database.


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There are limitations to using LC Subject Headings. No one research tool alone will give you all the results you need. The Subject Heading system is an extremely valuable tool, but just one among many that you need to be familiar with for in-depth research.

Here are some of the limitations of the LCSH system to be aware of:

1. The list of subject headings is not totally comprehensive, especially when it comes to newer topics and terms. So it's possible that there won't be a subject heading that precisely fits your topic. 

2. The Individual who selected the subject headings for an item chose the best ones that s/he could determine for it at the time. However, there is a certain amount of subjectivity in the selection process.

3. If you read the history of the development of the LCSH system in the next section, you'll learn that it was developed in the early 20th century. Some terms have been changed during the years to reflect current usage. However, some terms may not mean what you expect them to mean.

What are the limitations to using LC Subject Headings?


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What are the limitations to using LC 

Subject Headings?  (continued)  

4. The form of subject heading phrases will vary. For example,
     you'll find both "Theology, Practical" and "Process theology".

5. Article databases make modifications and additions so
     they'll have some indexing terms not in the LCSH.

6. Using LC Subject Headings does not guarantee that you'll find
     all you need. This system is just one tool among many.
     Sometimes you may need to combine a subject heading
     keyword with a general keyword or just use keywords. Research
     requires patience, creativity, and skill. Like anything else, the
     more you practice the skills, the better you'll be.


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Concluding Thoughts

I hope this booklet has helped you understand the system behind the Library of Congress Subject Headings. I hope, too, that you have come to appreciate the advantages of using the system, especially when you're having difficulty finding what you need using just general keywords. 

While the haystack of information is increasing exponentially, the size of the needle you're looking for is about the same as before and thus increasingly difficult to find. You need to continue to learn new skills for information discovery and to sharpen the skills you already have. 

Technology will continue to open vast new reservoirs of information that are accessible from smaller and smaller devices. But only those who have the skills will be able to make the most of the expanding universe of resources. 

Happy searching!


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Why was the LCSH system created?

The Library of Congress was established in 1800 as the legislative library for the United States Congress. The initial collection, housed in the capitol building, was comprised of 740 books plus three maps. Within a few years, borrowing privileges were extended to the President, members of his administration, most government agencies, and the judicial branch.


In 1814, the Capitol building was burned to the ground by the British, destroying the Library's collection which had grown to about 3,000 volumes. To restore the collection, Thomas Jefferson sold his personal library of almost 6,500 volumes to the Library. Because of the amazing breadth of his collection, the scope of the Library's mission and future collection development were expanded to now serve as a national library.


(continued on next page)



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The collection now began to mushroom, and the need for an organizing system became critical. The Library adopted the subject heading system developed by the American Library Association for smaller libraries but modified it for their unique purposes. This system has now grown to over 250,000 subject headings, with detailed notes and cross references. 


(Summarized from "Still Robust at 100: A Century of LC Subject Headings", By Lois Mai Chan. Images from the Library of Congress web site.)

Why was the LCSH system created? (continued)


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I welcome your comments 
and suggestions.


 Laura W. Harris, Retired


Last Position:

Reference & Instruction Librarian

Iliff School of Theology

Denver, Colorado 


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