McGregor D.C. Canadian and Australian Devonian spores : Zonation and correlation / D.C.McGregor,G.Playford, 1992. - 125 p. - Текст : непосредственный.
Playford G. Miospores and organic-walled microphytoplankton of devonian-caboniferous boundary beds (bakken formation), Southern Saskatchewan: a systematic and stratigraphic appraisal / G.Playford,D.C.McGregor, 1993. - 107 p. - Текст : непосредственный.