Ramzaeva, Natalya; Mittelbach, Cathrin; Seela, Frank Helvetica Chimica Acta, 1999, vol. 82, # 1 p. 12 - 18 doi: 10.1002/(SICI)1522-2675(19990113)82:1<12::AID-HLCA12>3.0.CO;2-L