Hilger, H. H., and U. R.  Böhle. 2000. ?Pontechium: a new genus distinct from Echium and Lobostemon (Boraginaceae)?. Taxon 49:737?746.

Mansion, G., F.  Selvi, A.  Guggisberg, and E.  Conti. 2009. ?Origin of Mediterranean insular endemics in the Boraginales: integrative evidence from molecular dating and ancestral area reconstruction?. Journal of Biogeography 36.