W. Edwin Clark: "It would be interesting to see a reference to a publication that denies that 1 is a factor of every integer." The 19th century arithmetic texts that I had occasion to look at all agreed that both the multiplicand and multiplier of a product were factors and generally gave examples in pairs that excluded the number itself multiplied by one. Edward Liddell in his Arithmetic for the Use of Schools (1860) made it explicit: "We have already learnt that when 6 and 8 are multiplied together they make the product 48. For this reason 6 and 8 are called factors of 48, from the Latin facio, which signifies to make. We may therefore separate or resolve 48 into the two factors 6 and 8, or into the two factors 4 and 12. The figure 1 is not regarded as a factor; consequently, in whole numbers, all factors are greater than unity." Eric Weisstein cites Ore's 1988 Number Theory and its History and Burton's 1989 Elementary Number Theory for his number theoretic usage that "a factor of a number n is equivalent to a divisor of n". He adds: "In elementary education, the term 'factor' is sometimes used to mean proper divisor, i.e., a factor of n other than the number itself. However, as a result of the confusion this practice creates and its inconsistency with the mathematical literature, it should be discouraged."