Template:Heard & Jones, 1931
- Heard, A.J. & Jones, J.F. 1931. A new plant (Thallomia) showing structure, from the Downtonian rocks of Llandovery, Carmarthenshire. Quarterly Journal of the Geological Society of London 87:551-562. DOI: 10.1144/GSL.JGS.1931.087.01-04.19