We study the homotopy decomposition problem for closed connected 4-manifolds with free fundamental groups. For this we apply obstruction theory and give a detailed description of Whitehead's exact sequence for the named class of manifolds.
A note on four-manifolds with free fundamental groups / Cavicchioli, Alberto; Hegenbarth, F.. - In: JOURNAL OF MATHEMATICAL SCIENCES UNIVERSITY OF TOKYO. - ISSN 1340-5705. - STAMPA. - 4:(1997), pp. 435-451.