A First Course in Complex Analysis
by Matthias Beck, Gerald Marchesi, Dennis Pixton, Lucas Sabalka · Orthogonal Publishing
Open textbook (CC BY 4.0, version 1.6) for a one-semester undergraduate course. It moves from complex differentiability and Cauchy's theorem to power series and the Residue Theorem, with over 250 exercises and SageMath prompts. Best free rigorous entry-level text; gives beginners a no-cost alternative to Conway (graduate level). A free PDF is available.
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