Gottschling, M., and H. H.  Hilger. 2003. ?First fossil record of transfer cells in angiosperms?. 90:957?959.

Diane, N., C.  Jacob, and H. H.  Hilger. 2003. ?Leaf anatomy and foliar trichomes in Heliotropiaceae and their systematic relevance?. Flora 198:468?485.

Clermont, A., E.  Zippel, and H. H.  Hilger. 2003. ?Verbreitung und Differenzierung der mitteleuropäischen Unterarten von Buglossoides arvensis (L.) I.M.Johnst. (Boraginaceae)?. Feddes Repert. 114:58?70.

Buys, M., and H. H.  Hilger. 2003. ?Boraginaceae cymes are exclusively scorpioid and not helicoid?. Taxon 52:719?724.

Hilger, H. H., and N.  Diane. 2003. ?A systematic analysis of Heliotropiaceae (Boraginales) based on trnL and ITS1 sequence data?. Bot. Jahrb. Syst. 125:19?51.