https://en.wikipedia.org/wiki/Implicational_propositional_calculus https://en.wikipedia.org/wiki/List_of_Hilbert_systems#Implicational_propositional_calculus https://en.wikipedia.org/wiki/List_of_first-order_theories https://openlogicproject.org/ https://builds.openlogicproject.org/ https://builds.openlogicproject.org/content/first-order-logic/first-order-logic.pdf