theorem Th5: :: CARD_5:5

for A being Ordinal
for X being set st X c= A holds
ex phi being Ordinal-Sequence st
( phi = canonical_isomorphism_of ((RelIncl (order_type_of (RelIncl X))),(RelIncl X)) & phi is increasing & dom phi = order_type_of (RelIncl X) & rng phi = X )