Bestmann, Hans Juergen; Liepold, Bernd; Kress, Anita; Hofmann, Andreas Chemistry - A European Journal, 1999, vol. 5, # 10 p. 2984 - 2989 doi: 10.1002/(SICI)1521-3765(19991001)5:10<2984::AID-CHEM2984>3.0.CO;2-8