A method for the choice of glasses in Taylor triplets, in which the glasses of the first and third lenses are different, is described. By using the conditions for total power, longitudinal chromatic aberration, Petzval sum, transverse chromatic aberration, and distribution of power between the first and third lenses, an equation for the power of the second lens in terms of the glass constants is derived. This equation forms the basis of the method, by which a glass combination is obtained giving a small power for the second lens. The length of the objective and the position of the diaphragm are taken into consideration during selection. A condition of distortion is also satisfied.
N. V. D. W. LESSING, "Selection of Optical Glasses in Taylor Triplets (General Method)," J. Opt. Soc. Am. 49, 31-33 (1959)