Complex sentence: Early forms of relation algebra emerged in the 19th century with the work of De Morgan, Peirce, and Schröder; its present-day purely equational form was developed by Tarski and his students starting in the 1940s.
Split into simpler sentences: Early forms of relation algebra emerged in the 19th century with the work of De Morgan, Peirce, and Schröder. Its present-day purely equational form was developed by Tarski and his students starting in the 1940s.