1829. Nat. Philos., Polaris. Light, vii. 24 (L.U.K.). The whole system of rings will appear to be like the uniaxal system.
1866. B. Stewart, Heat, § 43. Crystals that are optically uniaxal.
1881. Glazebrook, in Phil. Trans., CLXXIII. 595. The Surface of a Uniaxal Crystal.