Engineering Orientation

Many first perceive literature to be defined as creative works like fiction or or collections of poetry.  In scholarly and professional terms, literature is also defined as works available or published about a particular concept.  It is like a world of many types of publications and information!  The literature is commonly found in an index and database search, and used as references cited in a research publication.  See below for examples and explanations.

Professional literature falls under 3 categories, primary, secondary, and tertiary.  Within those categories are various types of publications.  See the table for their definitions, attributes and examples:

Reference Works 

A reference work is a collection of general facts within a field.  These can be used to find standards, measurements, or the general background of a theory.  Many types of reference works exist, but these are ones more commonly used in the sciences.

1. Handbook: a resource that summarizes major topics or processes within a field.  These often provide tables with equations, functions, algorithms, and other established measurements or methods. 
2. Standard:  a document with agreed-upon technical specifications or other criteria with the intention of being used as rules, guidelines, or definitions of characteristics to ensure that materials, products, processes, or services are fit for their purpose (International Organization for Standardization, n.d.).  A standard is established by a professional organization to provide a baseline of acceptable quality. See Engineers Edge list and description of standards from ANSI, ASTM, and others.
3. Encyclopedia: a collection of summaries on selected key concepts within a field.  Scholars often use one as an initial resource to learn about an unfamiliar topic. 

International Standard Organization (n.d).  Standards.  https://www.iso.org/standards.html 

Technical Notes & Patents 

Certain scientific fields communicate their findings using other types of publications:

1. Technical note:  a description of new technology and recent innovations.
2. Technical report:  an account of work done on a research project; often used for internal documentation within a company or institution.
3. Patent:  a public notice of an invention filed with a governmental patent agency.  A patent gives the inventor exclusive rights to his or her creation for a certain amount of time.  A patent document often provides technical information on a given work or form of technology.  It does not undergo the peer review process, but rather is a legal document.

Grey Literature

Gray (or grey) literature generally consists of publications that are not distributed through scholarly or commercial channels such as professional journals.  Types of gray literature may include:

• Trade reports
• Government publications
• Conference proceedings
• Company research or "white papers"

Some definitions of gray literature include publications such as blogs, statistical reports, and working papers.  

The purpose of gray literature varies and depends on the setting in which it is published and distributed.  In corporations or organizations, gray literature may be used to distribute new information, communicate for internal purposes, or to document activities.  One example is State Licensed Substance Abuse Treatment Programs in Philadelphia,  a report of The Pew Charitable Trust's study on medical-assisted treatment (MAT) and opioid-related deaths.  For academic contexts, gray literature may be a forum for presenting ideas that may be emerging or do not yet have wide interest. 

Gray literature should be considered in any literature review in order have a broader view of what is discussed and researched on a particular topic.

Commentaries & Letters to the Editor

The following document types are often retrieved in a database search.  These are generally known as "front material."  Although they do not communicate original research or generate new knowledge, their role is to provide an arena for commentary and discussion within a field:

1. Commentary:  an expert's response to a study based on his or her knowledge or experience to it.
2. Editorial:  a review or critique of articles within the featured issue of a journal, a brief discussion of a topic, or a notice of recent developments within a field.
3. Letters to the Editor:  also known as correspondence.  These are usually written in response to content featured in a journal.  They may be used to generate new ideas.

Other types of these documents include opinion pieces, news, and obituaries.