^Inc، Time (14 أكتوبر 1966). "LIFE". Time Inc. مؤرشف من الأصل في 2016-05-20. اطلع عليه بتاريخ 2016-12-04 – عبر Google Books. {{استشهاد ويب}}: |الأخير= باسم عام (مساعدة)
^piethein.comنسخة محفوظة 4 August 2010 على موقع واي باك مشين. "For a long time they appeared under the signature Kumbel Kumbell. Here is the reason why: Piet is the Dutch form of the name Peter or Petrus, which means rock, stone, and Hein is a way of spelling ‘hen’, the old Danish word for a whetstone. ‘Kumbel’, or ‘kumbl’ as it strictly speaking should be written, also means stone, though more a grave monument. In other words, Piet Hein, or Stone Stone can, in a way, be translated by Kumbel Kumbel. He originally wrote the second word with two Ls, also later the signature became just Kumbel – the name he is at least as well known by as his own."
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