The articles, usually written by scholars, often refer to key sources on the article's subject. Some are single volumes, while others are published in multivolume sets. Subject encyclopedias may be updated by supplements. Sometimes the word dictionary appears in the title, but the length of the articles indicate that the work is really an encyclopedia. Again remember to consult the index to locate information on a topic.
Subject encyclopedias are an excellent place to start research.
As sources, they are often overlooked. While they may not be included in a bibliography for a research paper, they provide information like names, dates, terms, and concepts that lead further into research on a topic. General dictionaries may be illustrated and contain special features like lists of proper names, maps, and tables of weights and measures. Unabridged dictionaries are large in size because they include all words in use at the time the dictionary is compiled. Abridged or desk and collegiate dictionaries are smaller and include only a selection of words.