The encyclopedia has remained a trusted source for students conducting research. The internet has increased the availability of free, quality encyclopedias and nearly any topic, though many encyclopedias that contain deep, specialized knowledge are still accessed primarily through universities or subscription services.

Encyclopedias for General Information

General encyclopedias cover a wide range of topics in the form of short articles written by knowledgeable experts. Due to the number of topics covered, the information contained in such volumes has limited depth but gives enough information to provide key words and possible sources for further research. Historically, general encyclopedias were alphabetized and printed in multivolume sets to be included in schools of all levels. More contemporary versions like Encyclopedia Brittanica are available online and regularly updated by content experts.

Subject-Specific Encyclopedias

If you're looking for depth on a topic or subject beyond what a general encyclopedia offers, then a subject-specific encyclopedia is your best bet. For instance, if you look up astronomy in a general dictionary, you will get some basic information on the history of astronomy and specific disciplines of the science. However, if you reference a subject-specific encyclopedia in this area, you can learn about topics like dark matter and supernovas in much greater detail. These encyclopedias also include bibliographies that help you track down specific books and articles related to your field of research. Many university libraries carry in-print and online versions of subject-specific encyclopedias like the Encyclopedia of Astronomy and Astrophysics and the Cambridge Encyclopedia of Astronomy.

Electronic Encyclopedias

We live in a digital world where information is available instantaneously and things change rapidly. To evolve with such a connected society, many encyclopedias have moved their print versions online while retaining a similar editorial staff and contributors that include experts in their respective fields. Such online knowledge bases allow students and teachers quick, up-to-date access wherever they are connected to the web, whereas expensive and heavy books serve as a barrier to some. World Book Online, for instance, offers a subscription-based version, and Scholarpedia is a free, peer-reviewed and online-only knowledge base.

Crowdsourced Encyclopedias

Crowdsourcing knowledge has become an easy way of accumulating information in the digital age. Online encyclopedias and forums, like Wikipedia, are popular places for amateurs and experts alike who wish to share their knowledge with the world. While some of these sources are criticized as having questionable credibility, others believe that the ability to have limitless people post, critique and fact check creates a reliable source of information. According to researchers at the University of California Irvine in 2010, articles that have been featured on Wikipedia had high-quality information 86 percent of the time, compared to nonfeatured articles that had a similar level of quality 74 percent of the time, so the quality of the content for such articles increases as they go through revisions. But before you jump right in, it's always a good idea to ask your teacher if you're allowed to use a crowdsourced encyclopedia as a source.