Letter from E.A. Tinbergen to her husband's family written just before sailing for Greenland (postmark on envelope, Copenhagen, 10 July 1932); three family letters from the Tinbergens, on board the 'Gertrud Rask', 10, 14 and 19 July 1932; postcard from T. van Lohuizen to the Tinbergen family, The Hague, 23 July 1932.