An extensive variety of closed n-manifolds N, called codimension-2 (orientable) fibrators, automatically induce approximate fibrations, in the sense that all proper maps ;In the second part of this dissertation, we study the behavior of codimension-2 fibrators under the connected sum operation. As a consequence, we will get the neat result on closed 4-manifolds as follows; Given a closed 4-manifold N which is a nontrivial connected sum of two 4-manifolds ;In the next section we determine which closed n-manifolds (
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