2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148184The structure of differential equations as they appear in special \K\ geometry of $N=2$ supergravity and $(2,2)$ vacua of the heterotic string is summarized. Their use for computing couplings in the low energy effective Lagrangians of string compactifications is outlined. (Talk presented at the Workshop on String Theory, April 8--10, 1992, Trieste, Italy)22 pages, CERN-TH.6580/92, (changed references)High Energy Physics - Theorytext