Three letters from Tinbergen to his parents written in the hostage camp where he was interned for a time during the Second World War. The first two are undated but attached to envelopes postmarked 11 and 23 September 1942 respectively, the third is dated 27 September 1942.

Letter from E.A. Tinbergen to Tinbergen's parents. Undated but from the time of Tinbergen's internment.