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\(\def\Z{\mathbb{Z}} \def\zn{\mathbb{Z}_n} \def\znc{\mathbb{Z}_n^\times} \def\R{\mathbb{R}} \def\Q{\mathbb{Q}} \def\C{\mathbb{C}} \def\N{\mathbb{N}} \def\M{\mathbb{M}} \def\G{\mathcal{G}} \def\0{\mathbf 0} \def\Gdot{\langle G, \cdot\,\rangle} \def\phibar{\overline{\phi}} \DeclareMathOperator{\lcm}{lcm} \DeclareMathOperator{\Ker}{Ker} \def\siml{\sim_L} \def\simr{\sim_R} \newcommand{\lt}{<} \newcommand{\gt}{>} \newcommand{\amp}{&} \)


Thank you to Jennifer Nordstrom of Linfield College for introducing me to the PreTeXt authoring system; to Rob Beezer at the University of Puget Sound for facilitating my entry into the PreTeXt world; to David Farmer at the Open Textbook Initiative for typesetting the initial draft of this book in PreTeXt; and to Rob, David, Mitch Keller, Alex Jordan, Bob Plantz, Alex Best, and everyone else otheir extensive technical help via the PreTeXt support group.