Kyung-ann Lee, et al. “Comparison of the Efficacy and Safety of Oligomeric Proanthocyanidins and Nifedipine in Patients With Primary Raynaud’s Phenomenon: An Open-Label, Randomized, Prospective Pilot Study”. Archives of Rheumatology, vol. 38, no. 3, Sept. 2023, pp. 477-9, doi:10.46497/ArchRheumatol.2023.9212.