| − | Unlike the general encyclopedia, the ''specialized encyclopedia'' covers a specific topic or subject, and often going into great detail not normally covered by a general encyclopedia. Appearing in the second half of the 20th century, these works were published in single or multi-volumes, and were usually sold in bookstores, though several, such as the various series by Time-Life, were sold via subscription. The subjects themselves were were enormously-varied, covering nations, history, wildlife, religion, photography, science, and so on. | + | Unlike the general encyclopedia, the ''specialized encyclopedia'' covers a specific topic or subject, and often going into great detail not normally covered by a general encyclopedia. Appearing in the second half of the 20th century, these works were published in single or multi-volumes, and were usually sold in bookstores, though several, such as the various series by Time-Life, were sold via subscription. The subjects themselves were were enormously-varied, covering nations, history, wildlife, religion, photography, science, and so on, of which a few examples are mentioned below: |