Investigation of the thin lens theory of zoom lenses results in a general statement concerning conjugate points, a simple proof of the maximum number of crossing points, and an algorithm for computing component focal lengths of a five-component symmetrical zoom lens. The three-component optically compensated zoom lens is discussed in detail. Results of applying the algorithm are given. A prototype of the five-component zoom lens has been built and is briefly discussed.
GLENN WOOTERS and E. W. SILVERTOOTH, "Optically Compensated Zoom Lens," J. Opt. Soc. Am. 55, 347-348 (1965)