Encyclopædia Britannica it is scarcely used, and reviewers have recommended that it be dropped from the encyclopaedia. The also has color transparencies of human anatomy and several appendices listing the staff members, advisors, and contributors to all three parts of the Britannica. Taken together, the and comprise roughly 40 million words and 24,000 images. The two-volume index has 2,350 pages, listing the 228,274 topics covered in the "Britannica", together with 474,675 subentries under those topics. The "Britannica" generally prefers British spelling over American; for example, it uses "colour" (not "color"), "centre" (not "center"), and "encyclopaedia" (not "encyclopedia"). However, there are exceptions to
Encyclopædia Britannica this rule, such as "defense" rather than "defence". Common alternative spellings are provided with cross-references such as "Color: "see" Colour." Since 1936, the articles of the "Britannica" have been revised on a regular schedule, with at least 10% of them considered for revision each year. According to one Britannica website, 46% of its articles were revised over the past three years; however, according to another Britannica web-site, only 35% of the articles were revised. The alphabetization of articles in the and follows strict rules. Diacritical marks and non-English letters are ignored, while numerical entries such as "1812, War of" are