History of the Encyclopædia Britannica the criteria by which the articles were sorted were not obvious even to scholars, despite Dr. Adler's claims that the sorting followed naturally from the "Propædia's" outline of all knowledge. In 1985, the "Britannica" responded to reader requests by restoring the index as a two-volume set. The number of topics indexed by the "Britannica" has fluctuated from 500,000 (1985, the same as in 1954) to 400,000 (1989,1991) to 700,000 in the current 2007 print version. Presumably, this recent increase reflects the introduction of efficient electronic indexing, since the size of the encyclopedia has remained nearly constant at approximately 40 million
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