For any worthwhile study in any field of knowledge the research worker needs sufficient familiarity with library and its many resources.
The search for reference material is time consuming but very fruitful phase of a research program. Every investigator must know what sources are available in his field of inquiry, which of them he is likely to use and where and how to find them.


According to L.R.Gay,
The review of related literature involves the systematic identification, location, and analysis of document containing information related to the research problem.
According to Fink (1998) Literature review is a systematic, explicit, and reproducible method for identifying, evaluating, and interpreting the existing body of recorded work produced by researchers, scholars, and practitioners.
Meaning and Importance
It is important to have a literature review because without it
1. you will not acquire an understanding of your topic,
2.of what has already being done on it,
3. how it has been researched, and
4. what the key issues are.
5. To give reasons why the topic is of sufficient importance for it to be researched

6. To provide the reader with a brief up-to-date account and discussion of literature on the issue relevant to the topic
7. To provide a conceptual and theoretical context in which the topic for research can be situated i.e. the limits and boundaries of your study
8. To discuss relevant researches carried out  the same topic or similar topics
 In writing, at some point,  you have to mention that
 1. you understand the previous research on your topic. This means you have understood the main theories in the subject area and
 2.  how they have been applied and developed, as well as the main criticism that have been made of work on the topic.
The review is therefore, a part of your academic development– of becoming an expert in the field
It provides a theoretical background to the study.
It reviews the means by which researcher establishes the link between what he is proposing to examine and what has already been studied. In simple words, it helps to refine research methodology.
Through the literature review researcher are able to show his finding has contributing to existing body of knowledge in his profession.
It enables researcher to contextualize his findings
The literature review demonstrate the under lying assumptions (i.e. proposition) behind the research question that are the central of research proposal.

The literature review provides the researcher with an opportunity to identify the gaps that may exist in the body of literature and to provide a rationale for how the proposed study may contribute to the existing body of knowledge.
The literature review helps the researcher to refine the researcher questions and embed them in guiding hypotheses that provide possible directions the researcher may follow
What is review of  literature?
A literature review is an account of what has been published on a topic by scholars and researchers.
when writing the literature review section, your purpose is to convey to your reader what knowledge and ideas have been established  and presented on a topic, what are the strengths and weaknesses of theses studies .
As a piece of writing, the literature review must be defined by a guiding concept. It is not just a descriptive list of the material available, or a set of summaries of the studies. writing a literature review lets you gain and demonstrate the skills  in two areas;

information seeking: the ability to scan the literature efficiently, using manual or computerized methods, to identify a set of useful articles and books

Critical appraisal: the ability to apply principles of analysis to identify unbiased and valid studies.

Some guidelines for writing an excellent systematic review of a study;
Øintroduction of the study (topic,author name)
Ø Objectives of the research
ØPopulation of the research
ØSample of the study and how the sample is selected.
ØMethodology of the study
Ø Tools of data collection

ØInstrument and analyses of the study
ØFinding and conclusion of the study
ØSuggestions  and recommendations of the study
ØCritical analysis of the study (what are the weaknesses of the study).

There are generally two types of sources.
1. Primary sources
2. Secondary sources

Primary source consists of literature reported by the individual(s) who actually conducted the research or who originated the ideas. Or we can say that direct source of information
Following are the types of direct source.
Periodical literature found in journals,
Books, monographs, yearbooks and bulletins,
Graduate, doctoral and other theses ,and
Certain miscellaneous sources-like government publications on education.
Primary sources are original materials. They are from the time period involved and have not been filtered through interpretation or evaluation. Primary sources are original materials on which other research are based. They are usually the first formal appearance of results in physical, print or electronic format. They present original thinking, report a discovery, or share new information.
Examples include:
Artifacts (e.g. coins, plant specimens, fossils, furniture, tools, clothing, all from the time under study);
Audio recordings (e.g. radio programs)
Internet communications on email
Interviews (e.g., oral histories, telephone, e-mail);
Journal articles published in peer-reviewed publications;
Newspaper articles written at the time;
Original Documents (i.e. birth certificate, will, marriage license, trial transcript);
Proceedings of Meetings, conferences and symposia;
Records of organizations, government agencies (e.g. annual report, treaty, constitution, government document);
Survey Research (e.g., market surveys, public opinion polls);
Video recordings (e.g. television programs);
Works of art, architecture, literature, and music (e.g., paintings, sculptures, musical scores, buildings, novels, poems).
Web site.

Secondary sources are less easily defined than primary sources. Generally, they are accounts written after the fact with the benefit of hindsight. They are interpretations and evaluations of primary sources. Secondary sources are not evidence, but rather commentary on and discussion of evidence. However, what some define as a secondary source, others define as a tertiary source. perception is everything

Secondary source, however, is literature that summarizes primary sources. It does not represent material published by original researcher or the creator of the idea. These sources also called indirect source of information.
Encyclopedia of education.
Education indexes.
Educational abstracts.
Bibliographies and directories.
Bibliographical references
Quotation sources
Miscellaneous other sources.

 Typically researcher will locate both primary and secondary sources. But it is best to report mostly primary sources. Primary sources present the literature in the original state and present the view point of the original author. Primary sources also provide the detail of original research better than secondary sources. Secondary sources are helpful as researcher begin his review, to explore and determine the range of material on a topic.

 Tertiary sources
Tertiary sources consist of information which is a distillation and collection of primary and secondary sources. they include encyclopedias, fact books and almanacs, guides and handbooks. Some secondary sources such as indexing and abstracting tools can also be considered tertiary sources.

As tertiary sources, encyclopedias and textbooks attempt to summarize and merge the source materials into an overview, but may also present subjective commentary and analysis (which are characteristics of secondary choices).

In the United Nations International Scientific Information System (UNISIST) model, a secondary source is a bibliography, whereas a tertiary source is a synthesis of primary source
Tertiary sources generally provide an overview or summary of a topic, and may contain both primary and secondary sources. The information is displayed as entirely factual, and does not include analysis or critique.
Tertiary sources can also be collections of primary and secondary sources, such as databases, bibliographies and directories.
 How useful are the following sources?

Journal articles: these are good especially for up-to-date information. Bear in mind, though, that it can take up to two years to publish articles. They are frequently used in literature reviews because they offer a relatively concise, up-to-date format for research, and because all reputable journals are refereed (i.e. editors publish only the most relevant and reliable research).
Books: books tend to be less up-to-date as it takes longer for a book to be published than for a journal article. Text books are unlikely to be useful for including in your literature review as they are intended for teaching, not for research, but they do offer a good starting point from which to find more detailed sources.
Conference proceedings: these can be useful in providing the latest research, or research that has not been published. They are also helpful in providing information on which people are currently involved in which research areas, and so can be helpful in tracking down other work by the same researchers
Government/corporate reports: many government departments and corporations commission carry out research. Their published findings can provide a useful source of information, depending on your field of study.
Newspapers: since newspapers are generally intended for a general (not specialized) audience, the information they provide will be of very limited use for your literature review. Often newspapers are more helpful as providers of information about recent trends, discoveries or changes, e.g. announcing changes in government policy, but you should then search for more detailed information in other sources.

Theses and dissertations: these can be useful sources of information. However there are disadvantages:
                     they can be difficult to obtain since they are not published, but are generally only available from the library shelf
2) the student who carried out the research may not be an experienced researcher and therefore you might have to treat their findings with more caution than published research.

Internet: the fastest-growing source of information is the Internet. It is impossible to characterize the information available but here are some hints about using electronic sources:
              bear in mind that anyone can post information on the Internet so the quality may not be reliable,
              the information you find may be intended for a general audience and so not be suitable for inclusion in your literature review (information for a general audience is usually less detailed)
              more and more refereed electronic journals (e-journals) are appearing on the Internet - if they are refereed it means that there is an editorial board that evaluates the work before publishing it in their e-journal, so the quality should be more reliable (depending on the reputation of the journal).
Magazines: magazines intended for a general audience (e.g. Time) are unlikely to be useful in providing the sort of information you need. Specialized magazines may be more useful (for example business magazines for management students) but usually magazines are not useful for your research except as a starting point by providing news or general information about new discoveries, policies, etc. that you can further research in more specialized sources.

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