theorem Lem13: :: MSAFREE5:89

for a being object
for S being non empty non void ManySortedSign
for s being SortSymbol of S
for X being non-empty ManySortedSet of the carrier of S
for x being Element of X . s
for t being Element of (Free (S,X)) st t . a = [x,s] holds
a in Leaves (dom t)