A group of bestselling authors including John Grisham, George R.R. Martin and Jodi Picoult filed an amended complaint adding Microsoft as a defendant in their lawsuit against OpenAI in Manhattan federal court late Monday, noting that Microsoft has invested billions of dollars in OpenAI and holds a significant stake in OpenAI’s for-profit arm.

The authors and co-plaintiff The Authors Guild, a professional organization for writers, are represented by Lieff Cabraser Heimann & Bernstein and Cowan, DeBaets, Abrahams & Sheppard in the proposed class action copyright infringement suit.