DISCLAIMER: Resources, text and information used in this worksheet have been adapted from their original forms. These materials, including any adaptations, remain the property of their respective copyright owners. They are used solely for educational and instructional purposes, with no intent of commercial gain or profit. The use of such materials is in accordance with the principles of fair use, under applicable copyright laws.  Adapted and created by: Alejandra E. Juárez Ostoa and Montserrat Aguilar Pérez ,for the 5° semester course of Diseño de Materiales (0521) for the Licenciatura en Lingüística Aplicada from ENALLT, UNAM.