Complex sentence: A group of seven doctors issued a public letter to Somers and her publisher, Crown, in which they state that the protocol is "scientifically unproven and dangerous" and cite Wiley's lack of medical and clinical qualifications.
Split into simpler sentences: A group of seven doctors issued a public letter to Somers and her publisher, Crown, criticizing the endorsement of Wiley's protocol. In the letter they state that the protocol is "scientifically unproven and dangerous" and cite Wiley's lack of medical and clinical qualifications.