1. S. D. Hudson, H.-T. Jung, V. Percec, W.-D. Cho, G. Johansson, The W. M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, OH 44106–7202, USA.
2. G. Ungar and V. S. K. Balagurusamy, Department of Engineering Materials and Centre for Molecular Materials, The University of Sheffield, Sheffield S1 3JD, UK.