let A be QC-alphabet ; :: thesis: for H being Element of QC-WFF A st H is universal holds
Subformulae H = (Subformulae (the_scope_of H)) \/ {H}
let H be Element of QC-WFF A; :: thesis: ( H is universal implies Subformulae H = (Subformulae (the_scope_of H)) \/ {H} )
assume H is universal ; :: thesis: Subformulae H = (Subformulae (the_scope_of H)) \/ {H}
then H = All ((bound_in H),(the_scope_of H)) by Th6;
hence Subformulae H = (Subformulae (the_scope_of H)) \/ {H} by Th90; :: thesis: verum