Response to Universal Classification System for Platelet-Rich Plasma (PRP): A Method to define the variables in PRP production. Issue 2 (March 2021) - Magalon, J; Abellan-Lopez, M; Brandin, T; Degioanni, C; Grimaud, F; Veran, J; Dignat George, F; Bertrand, B; Sabatier, F