The axioms of equational propositional logic E are listed in the order in which they are usually presented and taught. Note that, equivalence comes first. Note also that, after the first axiom, we take advantage of associativity of equivalence and write sequences of equivalences without parentheses.
((p == q)
== r) == (p == (q == r))
p == q ==
q == p
true == q == q
false == ~true
~(p == q)
== ~p == q
(p /== q) == ~(p == q)
(p \/ q) \/ r ==
p \/ (q \/ r)
p \/ q ==
q \/ p
p \/ p == p
p \/ (q == r) ==
p \/ q == p \/ r
p \/ ~p
p /\ q == p ==
q == p \/ q
p => q == p \/ q == q
p <= q == q => p
p /=> q ==
~(p => q)
p /<= q ==
~(p <= q)