"sister" . "sisterships" . "half-sister" . "half-sisters" . . "sister vessels" . "Sister ship" . . "Sister ship" . . "Sister ship" . "sister-ship" . "Half-sister" . . "sister ship" . "sisters" . "sister boats" . "sister submarine" . "sisters'" . "sister's" . "sister boat" . "sister ships" . "sistership" . "sister vessel" . "half sister" . "near-sister" .