Fleet tenders played crucial role to the Kriegsmarine's navel
operations during world war two, to supply there surface ships
and U-boats with fuel, ammunition's, replacement crew and
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