1. Mode of secretion of graptolite perdiderm in normal and retiolite graptolites;Bates,1986
2. Coal petrology. It's principles, methods and application;Bustin;Geol. Assoc. Can. Short Course Notes 3,1985
3. Invertebrate Paleontology and Evolution;Clarkson,1981
4. Die Bedeutung der Graptolithen-Fragmente im Paläozoikum von Soest-Erwitte für Stratigraphie und Inkohlung;Clausen;Fortschr. Geol. Rheinl. Westf.,1982
5. The fine structure of graptolite periderm;Crowther,1981