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Priority claimed from US06/775,826external-prioritypatent/US4730857A/en
Application filed by Hydril CofiledCriticalHydril Co
Publication of NO871958D0publicationCriticalpatent/NO871958D0/en
Publication of NO871958LpublicationCriticalpatent/NO871958L/en
Publication of NO170901BpublicationCriticalpatent/NO170901B/en
Publication of NO170901CpublicationCriticalpatent/NO170901C/en