2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/11226We present a new data analysis method to study rectangular T^3 ``small universes" with one or two of its dimensions significantly smaller than the present horizon (which we refer to as T^1- and T^2-models, respectively). We find that the 4 year COBE/DMR data set a lower limit on the smallest cell size for T^1- and T^2-models of 3000h^{-1} Mpc, at 95% confidence, for a scale invariant power spectrum (n=1).Proceedings from XXXIst Recontres de Moriond: Future CMB missions. 6 pages, with 3 figures, and cmb.sty included. Color figures and links at http://www.sns.ias.edu/~angelica/topology.htmlAstrophysicstext