Reference sources like dictionaries and encyclopedia are often the first secondary sources consulted in a research project like the third essay, and consultation of these resources can be a crucial phase in the definition of a topic. The preliminary research topics we formulate very often prove either impossibly broad or too minutely focused when we actually confront the complex reality of the research-source landscape. Consulting entries in dictionaries and encyclopedias is a good way to plot inter-relationships between concepts and phenomena and discover productive new configurations, or to quickly map out large and complex territory to find more narrow foci that can be satisfactorily engaged in a project of the proposed dimensions.
Wikipedia is a fascinating social experiment in crowd-sourced knowledge compilation and organization, and it is sometimes the case that a Wikipedia entry on a given topic will be at least as comprehensive, accurate and current as its counterparts in better established encyclopedic publications. Because, however, Wikipedia entries can be sumbitted and altered by anyone at any time, you have no way of knowing who authored the information you’re looking at, when it was last edited and by whom. This means that, as with other information resources on the Open Web, you can only afford to use a Wikipedia entry if you’re expert enough in the subject matter to independently assess the accuracy, objectivity and currency of sources in that area. Wikipedia entries can still be useful as points of departure when addressing an unfamiliar topic, especially if they are well documented and provide bibliographic references to their own source material. The entries themselves cannot be cited in academic work because they are unstable sources of unknown authorship. Entries in professionally published encyclopedia and other reference sources are written by people with advanced academic credentials in the relevant areas and are subjected to the editorial scrutiny of other qualified experts. They are therefore far less likely to contain inaccuracies, suffer from excessive bias or be otherwise misinformative.