/usr/share/doc/texlive-doc/latex/lshort-spanish/fuente/src/lshort-letter.tex is in texlive-lang-spanish 2015.20160223-1.
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1 2 3 4 | \documentclass[11pt,letterpaper,twoside]{book}
\usepackage{mylayout}
\input{lshort-base.tex}
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