Mnemonic - Articles http://www.bangor.ac.uk/~mas009/mystory.html . . .

3. This is to certify that Mr. Wim Klien from Amsterdam, the Netherlands, correctly extracted the thirteenth root of a one hundred digit number: 88008443440489299575219015772236417859411720052615 65487280650870412023307854274990144578442271602817 in a time of 1 minute and 28.8 seconds on Tuesday, 7th April 1981 at the National Laboratory for High Energy Physics, Tsukuba, Japan. The correct answer is 48757377.

What did you guess? Here are the answers. Victor Bruce was 82, Len Cullabine was 77 and Wim Klien was 69 when the above items were written.

The persons I have presented to you here are not imaginary characters taken from some work of fiction. All three were personally known to me. I met them, I observed them, I enjoyed their friendship and I questioned them extensively about their habits and life styles. With Wim Klien in particular, whom I first met in the late 1960s at the European High Energy Physics Research Center (CERN) in Geneva, I enjoyed a close friendship over many years. When he was 72 years old he came to stay with me and gave a dazzling performance of mental agility at the University of Wales, Bangor on Wednesday 8th May 1985. On that occasion he came within 2 seconds of breaking the world record for such mental arithmetic set by him earlier in Japan which was mentioned above and which was recorded in the Guinness Book of Records. . . .

Every faculty can be maintained and improved through use. Waiters who take orders acquire exceptional short term memories. People who taste wine develop highly sensitive palettes. My friend Wim Klien whom I mentioned in section (ii) above, when aged 72, could multiply 100 digit numbers in his head faster than a computer because, and only because, he constantly exercised his faculty to perform mental arithmetic. . . .