operator for joining search terms: "Search term 1" "Search term 2" The OR keyword is used for logical OR: "Search term 1" OR "Search term 2" A prefixed minus sign is used for logical NOT: "Search term 1" −"Search term 2" See also Binary number Boolean algebra (structure) Boolean algebras canonically defined Boolean differential calculus Booleo Heyting algebra Intuitionistic logic List of Boolean algebra topics Logic design Principia Mathematica Propositional calculus Relation algebra Three-valued logic Vector logic Notes References Further reading Bocheński, Józef Maria (1959). A Précis of Mathematical Logic''. Translated from the French and German editions by Otto Bird. Dordrecht, South Holland: D. Reidel. Historical perspective , several relevant chapters by Hailperin, Valencia, and Grattan-Guinness (xviii+212 pages) External links 1847 introductions Algebraic logic Articles with example code