for X being non empty disjoint_with_NAT set
for I being Element of (FreeUnivAlgNSG (ECIW-signature,X)) holds
( ex x being Element of X st I = root-tree x or ex n being Nat ex p being FinSequence of (FreeUnivAlgNSG (ECIW-signature,X)) st
( n in Seg 4 & I = n -tree p & len p = ECIW-signature . n ) )