home	news	documentation	specification		implementation
foreword	milestones	version 2	version 2	(background - core - applications)	library	(static LDDL directory)
citations	visibility	version 1	version 1	(static HELM directory)	helena

Informal description: ""

{λ[a:Prop] .​ λ[b:Prop] .​ λ[a1:a] .​ λ[b1:b]} .​ <{(b) .​ (a)} .​ iff > .​ {(λ[x:b] .​ a1) .​ (λ[x:a] .​ b1) .​ (b) .​ (a)} .​ iffi

Validation parameters: sort hierarchy = "Z2", kernel options = ""