> as lemmas

1868 Philos. Trans. (Royal Soc.) 158 192 In this case the integral remains unchanged in value, if it extend over any Cartesian oval whose internal foci are FF′, and whose axis is 2a.

1877 B. Williamson Elem. Treat. Integral Calculus (ed. 3) viii. §166 The arc of a Cartesian Oval.

1941 Amer. Math. Monthly 48 496 The non-degenerate quartic is related rather intimately with the class of curves known as cartesian ovals.

1977 Proc. Royal Soc. B. 196 209 Clarkson & Levi-Setti (1975) have proposed that the spherical aberration of Trilobite eyes is removed by a non-spherical refracting interface (a ‘Cartesian Oval’) in the lens.