Aspidella poster references

Should you wish to consult the literature referred to in my Aspidella poster at the ISECT 2017 conference, it is as follows:

Billings, E. 1872: On some fossils from the Primordial rocks of Newfoundland. Naturaliste Canadien, 6, p. 465-479.
Boyce & Reynolds (2008):
Gehling et al. (2000):
Menon et al. (2013):