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Может, у кого есть бумажные книги по истории математических обозначений?
The expression "plus or minus" is very old, having been in common use by the Romans to indicate simply "more or less". It is often found on Roman tombstones, where the age of the deceased is given as illustrated to indicate "94 years, more or less".
Plus-or-minus symbol (±) was used by William Oughtred (1574-1660) in Clavis Mathematicae, published in 1631 (Cajori vol. 1, page 245).
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