Problematica bibliography

Briggs, D. E. G., and Conway Morris, S., 1986, Problematica from the Middle Cambrian Burgess Shale of British Columbia, in Hoffman, A., and Nitecki, M. H., eds., Problematic Fossil Taxa: New York, Oxford University Press, p. 167-183.

Rozanov, A. Y., 1986, Problematica of the Early Cambrian, in Hoffman, A., and Nitecki, M. H., eds., Problematic Fossil Taxa: New York, Oxford University Press, p. 87-96.