Academic or Specialized Encyclopedias
These definitions are based on information from Katz, William A. Introduction to Reference Work. New York: McGraw-Hill, 1997. Print.
Not everything is on the open Internet through search engines such as Google.
Many information sources such as reference materials, periodical articles, and books were first published in print, but now books and article begin their lives in a computer and are born digital and can be made available online. There are public and private areas of the Internet. Google, Yahoo and Bing cannot find the private areas of information with a logon and password.