N.V. Werf Gusto Firma v/h A.F. Smulders was a Norwegian shipbuilding
company, located in Schiedam, Ships and U-boats built by N.V.
Werf Gusto Firma v/h A.F. Smulders include.
German Warships, 1815-1945: Major Surface Vessels.
German Warships, 1815-1945: U-boats and Mine Warfare Vessels.
German warships of the Second World War.
For a complete list of sources