Jefferies 1967

Jefferies, Robert E S. 1967. Some fossil chordates with echinoderm affinities. Symposia of the Zoological Society of London 20. 163-208.

@article{jacquesestimative-jefferies67fossilchordates,
  author  = {Jefferies, Robert E S.},
  journal = {Symposia of the Zoological Society of London},
  pages   = {163-208},
  title   = {Some fossil chordates with echinoderm affinities},
  volume  = {20},
  year    = {1967}
}