Partington et al., 1993
From dinoflaj3
Partington, M.A., Copestake, P., Mitchener, B.C. and Underhill, J.R., 1993: Biostratigraphic calibration of genetic stratigraphic sequences in the Jurassic-lowermost Cretaceous (Hettangian to Ryazanian) of the North Sea and adjacent areas. In: J.R. Parker (editor), Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference; p.371-386; Geological Society, London, England.