Vinther, J., Smith, M., & Harper, D. (2011). Vetulicolians from the Lower Cambrian Sirius Passet Lagerstatte, North Greenland, and the polarity of morphological characters in basal deuterostomes. Palaeontology, 54(3), 711-719. https://doi.org/10.1111/j.1475-4983.2011.01034.x