W. B. Herapath (1852). "XXVI. On the optical properties of a newly-discovered salt of quinine, which crystalline substance possesses the power of polarizing a ray of light, like tourmaline, and at certain angles of rotation of depolarizing it, like selenite". Phil. Mag.3 (17). London: Taylor & Francis: 161–173. doi:10.1080/14786445208646983.
