This article develops elementary facts about a family of formal calculi called '''propositional equation reasoning systems''' ('''PERS'''). This work follows on the ''alpha graphs'' that [[Charles Sanders Peirce]] devised as a graphical syntax for [[propositional calculus]] and also on the ''calculus of indications'' that George Spencer Brown presented in his ''Laws of Form''.
+
This article develops elementary facts about a family of formal calculi described as '''propositional equation reasoning systems''' ('''PERS'''). This work follows on the ''alpha graphs'' that [[Charles Sanders Peirce]] devised as a graphical syntax for [[propositional calculus]] and also on the ''calculus of indications'' that George Spencer Brown presented in his ''Laws of Form''.