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mitutoyo.com
"The History of Gauge Blocks"(PDF). mitutoyo.com. Mitutoyo Corporation. 2013. p. 8. Archived(PDF) from the original on 2013-08-14. Retrieved 2020-02-01.
web.archive.org
"The History of Gauge Blocks"(PDF). mitutoyo.com. Mitutoyo Corporation. 2013. p. 8. Archived(PDF) from the original on 2013-08-14. Retrieved 2020-02-01.