Sarikaki V, Rallis M, Tanojo H, Panteri I, Dotsikas Y, Loukas YL, Papaioannou G, Demetzos C, Weber S, Moini H, et al. In vitro percutaneous absorption of pine bark extract (pycnogenol) in human skin. Journal of Toxicology - Cutaneous and Ocular Toxicology [Internet]. 2004;23(3):149 - 158.