1. Airy; Cambr. Phil. Trans. 6, 379, 1838.
2. Strutt (Lord Rayleigh): Phil. Mag. (4) 41, 107, 247, 447, 1871;
3. Strutt (Lord Rayleigh): Phil. Mag. (5) 9, 410, 1879.
4. K. Strehl: Theorie des Femrohrs usw. Teil I. Leipzig 1894.
5. Lambert: Photometria. Augsburg 1760.