Categories of Information Sources

Information resources are broadly divided into two categories, namely:

(i) Documentary Sources; and
(ii) Non Documentary Sources

Classification of Documentary Sources: The documentary sources of knowledge are classified into various categories by different writers such as C. W. Hanson, Denis Grogan, George S. Bonn and Linda C. Smith, R. S. Giljarevskij, Subramanyam and Dr. S. R. Ranganathan. Some of the notable classifications are listed below:

Classification of Documents by Denis Grogan

The classification of documentary sources advocated by Hanson and Grogan are mainly based on the ‘information characteristics’ of documents. H. W. Hanson (1971) divides documents into two categories - primary and secondary sources. Denis Grogan (1981) goes further and categorizes them as Primary, Secondary and Tertiary sources.

        i.    Primary Sources: - There are the sources of original investigation representing new knowledge or new interpretation of old knowledge. Often a primary document may be the only source of information in existence. Such a literature is difficult to locate and contains original, unfiltered, unorganized and scattered information. However, Grogan classified documents relating to scientific literature only. Hence, periodicals here mean scientific periodicals; research reports mean scientific research reports, etc.

Examples: Scientific periodicals, Research reports, Conference Proceedings, Patents, Standards, Trade Literature, Official Publications,  Theses and Dissertations, Reprints, Preprints, Laboratory Notebooks, Diaries, Memoranda, Internal Research Reports, Medical Records, Minutes of Meetings, Company Files, Personal Files, Correspondence, etc.

      ii.  Secondary Sources: - These sources compile or repackage the original existing knowledge from primary sources. They do not carry new and original information but guides users to primary documents. These are selected and well-organized sources, arranged according to some convenient artificial plan of arrangement depending upon their possible use. In short, they provide digested information and serve as a bibliographical tool to primary sources of information.

Examples:  Indexing and abstracting periodicals, Bibliographies, Current Awareness Bulletin, List of Research in Progress, Reviews, State-of-the-Art Reports, Technical Translations, Treatises, Monographs, Textbooks, Reference sources (Dictionaries, Encyclopedias, Handbooks, Manuals, Almanacs, Directories, Maps, Atlases, Biographical sources, Geographical sources), and Bibliographic Databases, etc.

    iii.    Tertiary Sources: These sources contain information distilled, compiled and collected from primary and secondary sources and serve as key to users in locating and using primary and secondary sources. Tertiary sources do not carry subject information but guide the users to the source where information on that subject is available. Hence, the main function of tertiary sources is to help the searcher to select right primary or secondary source.

Examples: Union Catalogues, Bibliography of bibliographies, Guides to literature, Directory of directories, Guides to reference sources, etc.

Classification of Documentary Sources by S. R. Ranganathan

Unlike ‘Information characteristics’ as considered by Denis Grogan (1982) and C. W. Hanson (1971) for the categorization of documentary sources, S. R. Ranganathan has classified documentary sources of information from two different angles:

a)      by the volume of thought content; and
b)      by recording media or ‘physical characteristics’ of documents.

According to volume of thought content, Ranganathan divided documents as (a) Macro document: documents that reflect macro thoughts such as books, monograph, thesis, dissertation etc.; and (b) Micro documents: Those documents embodying micro thoughts such as journal articles.

However, according to the ‘physical characteristics’ or ‘recording media’ he classified documents into four categories. These four categories also reflect the chronological order of their development. They are:

        i.      Conventional documents: Conventional documents are those which are generally recorded on paper in a natural language by writing, typing, printing or some other near-printing methods. These are the documents that are most common in use. Examples: books, periodicals, maps, atlases, etc.

      ii.         Neo-Conventional documents: According to Ranganathan, Neo-Conventional documents are a new class of micro-document, such as standards, specifications, patents, data of properties in natural sciences and their applications, reaction formulas and press cuttings of current opinion and news on social sciences, and science etc

    iii.              Non-Conventional documents: Non-Conventional documents are micro reproduction of conventional documents, prepared with using new techniques and non- conventional size, shape or media of recording. Examples: microfilms, micro-prints, and audio-visual documents, etc. 

    iv.      Meta-documents: Under this group Dr. Ranganathan included documents, which are produced by the direct recording of social or natural phenomena, using some instruments. These documents are recorded directly unmediated by the human minds with the use of instrument technology, photography, radar and various other elements. Examples: photographs, Fax etc.


Pamphlets: According to UNESCO’s definition "a pamphlet is a non-periodical printed publication of at least 5 but not more than 48 pages, exclusive of the cover pages, published in a particular country and made available to the public.". It is usually printed  with large fonts and colourful illustrations and provide information on a topic in simple language and are meant for wide range of users. 

Books: According to UNESCO's definition, "a book is a non-periodical printed publication of at least 49 pages, exclusive of the cover pages, published in the country and made available to the public". According to the intellectual content, books can be categorized as textbooks, monographs, treatises and reference books, etc.

Treatises: A treatise comes under secondary source of information. A treatise is ‘a long, formal piece of writing about a particular subject’. It is like an essay but longer. In other words, it is a formal, long written article or book that deals with the facts, evidence and conclusions on a specific subject. Examples: A Treatise on Heat by M. N. Saha and B. N. Srivastava. Prolegomena to Library Classification by S. R. Ranganathan, 1937 is also a treatise on classification theory and an infallible source of information on the subject.

Monographs: A monograph is a detailed and scholarly study of a single specialized subject or an aspect of a subject or on a person, and is usually accompanied with a bibliography. A monograph usually portrays an overall picture of the topic.

Dictionaries: The word ‘dictionary’ is derived from the Medieval Latin word ‘dictionarium’ meaning ‘collection of words or phrases’ or late Latin ‘dictionarius’, meaning ‘of words’. A dictionary is ‘a list of words of a language in alphabetical order and explains what they mean or gives a word for them in a foreign language’ [Hornby]. General dictionaries may be monolingual (single language used), bilingual or multilingual. The coverage of dictionaries varies: Abridged or Unabridged. 

Examples: The unabridged edition of Webster’s Third New International Dictionary of the English Language (1st edition, 1961) The Concise Oxford Dictionary (1st edition, 1911), 12th ed, 2011. Dictionaries devoted to specific subjects are called subject dictionaries.

Encyclopedias: Encyclopedia is a reference book or set of books providing summaries of knowledge either from all subjects or from a particular field or discipline and typically arranged alphabetically. The term ‘encyclopaedia’ is derived from the Greek ‘enkyklios paideia’, meaning ‘general education’, or ‘an all-around education’. Encyclopedia is regarded as supplement to all types of reference sources. Two major kinds of Encyclopedia are:  

General Encyclopedias: Examples: The Encyclopaedia Britannica (1st edition, between 1768 -1771, 3 vols).   Last print edition of the New Encyclopedia Britannica (15th edition reprint) is published in 2010 in 32 volumes. The 32 volume set is divided into 4 parts – Micropedia (12 volumes); Macropedia (17 volumes), Propedia (1 volume) and Index (2 volumes). Later in 2012, it was announced to cease the publication of print version in future.

Encyclopedia Americana is one of the largest general encyclopedias in the English language, first published between 1829-1933 as 13 volumes by Francis Lieber. The encyclopedia was purchased by Grolier in 1945. Following the acquisition of Grolier in 2000, the encyclopedia has been produced by Scholastic Corporation, New York. The most recent print edition of the Encyclopedia Americana was published in 2006 in 30 volumes by Scholastic Corporation.

Subject Encyclopedias: A subject encyclopedia is devoted to a particular subject like Library and Information Science or more than one subject like science and technology.

Examples: The Encyclopedia of Library and Information Science. 1st edition, Vol. 1-73. 1968-2003. Edited by Allen Kent, Harold Lancour and Jay E. Daily. New York: Marcel Dekker.

The second edition of The Encyclopedia of Library and Information Science edited by Miriam A. Drake was published in 2003 in 4 volumes; third edition edited by Marcia J. Bates and Mary Niles Maack came out in 2010 in 7 volumes. The most recent print edition of The Encyclopedia of Library and Information Science, fourth edition edited by John D. McDonald and Michael Levine-Clark published by CRC Press in 2017 in 7 volumes.

McGraw-Hill Encyclopedia of Science and Technology, 1st edition, New York: McGraw-Hill, 1960, 15 volumes.The most recent print edition of the ‘McGraw-Hill Encyclopedia of Science and Technology’ is 11th edition, published in 2012 comprising 20 volumes.


Grogan, Denis (1982). Science and Technology: An Introduction to the Literature. 4th ed. London: Clive Bingley.

Hanson, Christopher Wharton (1971). Introduction to Science Information Work. Aslib, 208 p.

Bonn, G. S. and L. C. Smith. “Literature of science and technology.” McGraw-Hill Encyclopedia of Science and Technology. 8th ed. New York: McGraw-Hill, 1997. pp. 139-145.

Self-Check Exercises

1. Ranganathan has categorized sources of information into __.

Answer: (C) Four
Notes: Conventional, Neo-Conventional, Non-Conventional and Meta Documents.

2. C. W. Hanson has categorized documentary sources of information into __.

Answer: (A) Two
Notes: C. W. Hanson (1971) in the article 'Introduction to science Information work' published in ASLIB proceedings, divides documentary sources of information into two categories i.e. Primary and Secondary.

3.Who classified documentary sources of information into three broad categories?

Answer: (B) Denis Grogan
Notes: Denis Grogan has classified the documents into three categories, namely: primary, secondary and tertiary. Notes: Master Moti Lal Sanghi was famous for providing door to door free book service called as Dasti Pustak Sewa and for which the book were acquired from his personal resources.

4. According to Ranganathan, 'audio-visual materials, micro-prints and microfilms come under __.

Answer: (C) Non-conventional

5. According to Ranganathan, 'Patents, Standards, and Specifications', come under __.

Answer: (B) Neo-Conventional

6. According to Ranganathan, 'Photographs' comes under __.

Answer: (D) Meta-Documents

7. According to Ranganathan, 'Books, Periodical Publicaitons, Maps, Atlas, etc.' comes under __.

Answer: (A) Conventional

8. 'IndCat' is an example of __.

Answer: (C) Tertiary sources

9. According to Ranganathan, 'Documents produced by direct recording of social or natural phenomena using some instruments' is called:

Answer: (D) Meta-Documents

10. 'Bibliography of Bibliographies' is a __ source of Information.

Answer: (C) Tertiary

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