Walker, Rebecca L.: The good life for non-human animals. What virtue requires of humans. In: Working Virtue. Virtue Ethics and Contemporary Moral Problems. Hrsg. v. Rebecca L. Walker/ Philip J. Ivanhoe. Oxford 2007. Internet: https://books.google.de/books?id=tk0VDAAAQBAJ&printsec=frontcover&dq=Working+Virtue.+Virtue+Ethics+and+Contemporary+Moral+Problems.&hl=en&sa=X&ved=0ahUKEwjh89v8nKHTAhVCthQKHXd7BLwQ6AEIJDAA#v=onepage&q&f=false. S. 173–189.