- Nepohualtzintzin The Pre Hispanic Computer Quote: "...The Nepohualtzintzin is an instrument, similar to the abacus or soroban, that serves to make arithmetical and mathematical calculations..."
- Maya site: Nepohualtzintzin
- Webarchive backup: Mesoamerican abacus (Please be patient - it takes some time to load the picture) Quote: "...And lastly, the evident similarities in the design of the Chinese Solid & Broken Bar and Mesoamerican Bar & Dot number symbols is suggestive of some sort of relationship between the two systems. What that relationship may be is not clear, but it is hoped that further research will reveal its nature..."
- A Comparison of the Organization and Use of Chinese and Mesoamerican Abaci Citat: "...The remains of a 3/4 vigesimal1 (base twenty number system) abacus were purportedly found in Mexico. Whether or not this is true, the fact remains that the Mesoamerican bar-and-dot number signs appear to fit very systematically into such an arrangement, as demonstrated below..."
- Webarchive backup: Mayan Abacus Display (and Aztec)
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