Electron impact ionization studies with the amino acid valine in the gas phase and (hydrated) in helium dropletsS. Denifl, I. Mähr, F. Ferreira da Silva, F. Zappa, T. D. Märk and P. ScheierEur. Phys. J. D, 51 1 (2009) 73-79DOI: https://doi.org/10.1140/epjd/e2008-00092-4