1. Google Research, 1600 Amphitheatre Parkway, Mountain View, California 94043, United States
2. R&D Department, Philochem AG, Otelfingen, Zürich 8112, Switzerland
3. Philogen S.p.A., Siena 53100, Italy
4. Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH Zürich), Zürich 8092, Switzerland