Heilmann-Clausen, 1985
From dinoflaj3
Heilmann-Clausen, C., 1985: Dinoflagellate stratigraphy of the uppermost Danian to Ypresian in the Viborg I borehole, central Jylland, Denmark. Danmarks Geologiske Undersøgelse, Serie A, no.7, p.1-69, pl.1-15.