²The terms Cartesian and Jeffreys quantities were coined by Mosegaard and Tarantola (2002, doi:10.1016/S0074-6142(02)80219-4), in honour of French mathematician René Descartes and British geophysicist Sir Harold Jeffreys. They are also referred to as balances and amounts, respectively, by Mosteller and Tukey (1977, ISBN:0-201-04854-X).