Since the sum of two FSISs is not necessarily a closed subspace, the conditions should be imposed on the closure of the sum.
Conditions that guarantee that the sum of two FSISs is closed are described in Section 6.
In particular, if S and S' are FSISs, then [bar.S + S'] is an FSIS and
Since the subspaces [bar.S.sub.[gamma],[theta]] are FSISs, the fiber spaces [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] are finite-dimensional.
Then we apply the results to the class of FSISs in [L.sup.2]([R.sup.n]).