BIBLIOGRAPHY
Wikipedia「Russian ruble」「Grivna」「Decimalisation」
Wikipedia (according to the sources of each article)

Claims Supported by This Source
- According to one theory, "ruble" comes from the word "to chop," referring to a piece chopped from a silver grivna.
- A kuna was a marten pelt, and a veksha was a squirrel pelt ("Grivna", Russian version "Векша").
- In 1704, 1 ruble = 100 kopeks ("Decimalisation" cites Novgorod in 1534).
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