theorem Th97: :: MSAFREE5:130

for S being non empty non void ManySortedSign
for X being non-empty ManySortedSet of the carrier of S
for t being Element of (Free (S,X))
for f being vf-sequence of t
for B being FinSequence of the carrier of S st B = pr2 f holds
pr1 f is b₅ -sorts FinSequence of Union X