Revised structures for pluviatilol, methyl pluviatilol and xanthoxylol: General methods for the assignment of stereochemistry to 2, 6-diaryl-3, 7-dioxabicyclo [3.3. 0] octane lignans - Pelter, A; Ward, R S; Rao, E V; Sastry, K V (Tetrahedron, 1976)