We show the admissibility for of a rule form of the characteristic implicational axiom of abelian logic, this rule taking us from to . This is done in Section 8, with surrounding sections exploring the admissibility and derivability of various related rules in several extensions of .
"An Abelian Rule for BCI—and Variations." Notre Dame J. Formal Logic 57 (4) 551 - 568, 2016. https://doi.org/10.1215/00294527-3679398