Logical connective - WikipediaHistory of notations[edit] Negation: the symbol appeared in Heyting in 1930[3][4] (compare to Frege's symbol ⫟ in his Begriffsschrift[5]); the symbol appeared in Russell in 1908;[6] an alternative notation is to add a horizontal line on top of the formula, as in ; another alternative notation is to use a prime symbol as in . Conjunction: the symbol appeared in Heyting in 1930[3] (compare to Peano'
