Let x0 of type ι be given.
Let x1 of type ι → ι → ο be given.
Let x2 of type ι → ο be given.
Let x3 of type ι be given.
Apply unknownprop_dfe4c42452cb595dd82588e02161b9dace355d519e1ee3056b736fab3e836d01 with
e4ab3.. x0 x1 x2 x3,
x0,
x1,
x2,
x3.
Let x4 of type ι → ι → ο be given.
The subproof is completed by applying H0.