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Informal description: ""

{λ[a:Prop] .​ λ[b:Prop] .​ λ[n:(a) .​ not ] .​ λ[m:(b) .​ not ]} .​ <{(b) .​ (a)} .​ iff > .​ {({(m) .​ (a) .​ (b)} .​ th2 ) .​ ({(n) .​ (b) .​ (a)} .​ th2 ) .​ (b) .​ (a)} .​ iffi

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