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pra-

At a meeting in Stockholm in 1930, Sub-Committee 2 of the Advisory Committee on Nomenclature of the International Electrotechnical Commission recommended that this prefix (standing for practical) be attached to all practical units derived from the cgs system. The recommendation went no further.

International Electrotechnical Commission.
Recommendations in the field of quantities and units used in electricity. (1st ed.)
IEC Publication 164.
Geneva, 1964.
Page 27.