https://www.academia.edu/22468375/Commentary_on_the_Separate_Prologues_by_Humberto_Maturana_and_Francisco_Varela_to_the_Second_Edition_of_De_M%C3%A1quinas_y_Seres_Vivos-Autopoiesis_La_organizaci%C3%B3n_de_lo_vivo_-Twenty_Years_After?email_work_card=title