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In page La Voisin:

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The art of poisoning had become a regular science at the time,[citation needed] having been perfected, in part, by Giulia Tofana, a professional female poisoner in Italy, only a few decades before La Voisin. La Voisin provided a large variety of poisons for her clients and had a network of poison providers working for her, notably the apothecary Catherine Trianon.[1]