NMR study of fumarprotocetraric acid, a complex lichen depsidone derivative from Cladonia furcata - Su,B.; Cuendet,M.; Nikolic,D.; Kristinsson,H.; Ingolfsdottir,K.; Van Breemen,R.B.; Fong,H.HS.; Pezzuto,J.M.; Kinghorn,A.D. (Magn Reson Chem, 2003)