Purpuric ulcers associated with COVID-19: A case series - Sidharth Chand, BA; Renajd Rrapi, BA; Jennifer A. Lo, MD, PhD; Sarah Song, BS; Colleen K. Gabel, BS; Niyati Desai, MD; Mai P. Hoang, MD; Daniela Kroshinsky, MD, MPH (Elsevier, 2021)