↑ piethein.comLưu trữ 2010-08-04 tại Wayback Machine "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."
↑ Inc, Time (ngày 14 tháng 10 năm 1966). “LIFE”. Time Inc. Truy cập ngày 4 tháng 12 năm 2016 – qua Google Books.
