M.  Schultz and Büdel, B., ?Key to the genera of the Lichinaceae?, The Lichenologist, vol. 34, pp. 39-62, 2002.

M.  Schultz and Büdel, B., ?On the systematic position of the lichen genus Heppia?, The Lichenologist, vol. 35, pp. 151-156, 2003.