premise: During this period, two hardcover versions of the Addenda Sections were published' 6,000 Words (1976) and 9,000 Words .  Now the hardcover version of the 7873-main-entry 1986 Addenda Section, appearing simultaneously as 12,000 Words (1986), permits an updating of the statistics.
hypothesis: The 1986 Addenda Section covers a range of mathematical calculations.