1. Anonymous (2012) Call of the wild. De Economist 22:111–114
2. Attfield R (1981) The good of trees. J Value Enq 15:35–54
3. Attfield R (1991) The ethics of evironmental concern. University of Georgia Press, Athens
4. Bach N, Thung SN, Schaffner F (1989) Comfrey herb tea-induced veno-occlusive disease. Am J Med 87:97–99
5. Barnes J, Anderson LA, Phillipson JD (2002) Herbal medicines. A guide for healthcare professionals. Pharmaceutical Press, London