Harker and Sarjeant, 1991
From dinoflaj3
Harker, S.D. and Sarjeant, W.A.S., 1991: Late Cretaceous (Campanian) organic-walled microplankton from the interior plains of Canada, Wyoming and Texas: validation of new taxa. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, no.12, p.707-710.