(Reuters) -Microsoft has been hit with a lawsuit by a group of authors who claim the company used their books without permission to train its Megatron artificial intelligence model. Kai Bird, Jia Tolentino, Daniel Okrent and several others alleged that Microsoft used pirated digital versions of their books to teach its AI to respond to human prompts. The complaint against Microsoft came a day after a California federal judge ruled that Anthropic made fair use under U.S. copyright law of authors' material to train its AI systems but may still be liable for pirating their books.