https://www.wartsila.com/media/news/12-03-2009-wartsila-and-ihi-marine-united-sign-co-operation-agreement-for-efficient-propulsion-system-based-on-contra-rotating-propellers
Wärtsilä and IHI Marine United sign co-operation agreement for efficient propulsion system based on...
ihi marine unitedoperation agreementpropulsion systemsignefficient