F.  Luebert and Hilger, H. H., ?Typification of Heliotropium and Tournefortia (Heliotropiaceae) species described by Ruiz and Pavón?, Anales del Jardín Botánico de Madrid, vol. 71, p. e012, 2014.

P.  Pliscoff, Luebert, F., Hilger, H. H., and Guisan, A., ?Effects of alternative sets of climatic predictors on species distribution models and associated estimates of extinction risk: A test with plants in an arid environment?, Ecological Modelling, vol. 288, pp. 166?177, 2014.

F.  Luebert, Jacobs, P., Hilger, H. H., and Muller, L. A. H., ?Evidence for nonallopatric speciation among closely related sympatric Heliotropium species in the Atacama Desert?, Ecology and Evolution, vol. 4, no. 3, pp. 266?275, 2014.

M.  Gottschling, Hilger, H. H., Wolf, M., and Diane, N., ?Secondary structure of the ITS1 transcript and its application in a reconstruction of the phylogeny of Boraginales?, Plant Biology, vol. 3, no. 6, pp. 629?636, 2001.

N.  Diane, Hilger, H. H., and Gottschling, M., ?Transfer cells in the seeds of Boraginales?, Botanical Journal of the Linnean Society, vol. 140, no. 2, pp. 155 - 164, 2002.

H. H.  Hilger and Zippel, E., ?"Studies in the Boraginaceae": An index to the publications of Ivan M. Johnston dealing with the Borage family?, Haussknechtia Beiheft, vol. 11, pp. 1 - 151, 2001.

F.  Luebert, Hilger, H. H., and Weigend, M., ?Diversification in the Andes: Age and origins of South American Heliotropium lineages (Heliotropiaceae, Boraginales)?, Molecular Phylogenetics and Evolution, vol. 61, no. 1, pp. 90 - 102, 2011.

H. H.  Hilger, Gottschling, M., Selvi, F., Bigazzi, M., Långström, E., Zippel, E., Diane, N., and Weigend, M., ?The Euro+Med treatment of Boraginaceae in Willdenowia 34 ? a response?, Willdenowia, vol. 35, pp. 43 - 48, 2005.

M.  Gottschling, Diane, N., Hilger, H. H., and Weigend, M., ?Testing hypotheses on disjunctions present in the Primarily Woody Boraginales: Ehretiaceae, Cordiaceae, and Heliotropiaceae, inferred from ITS1 sequence data?, International Journal of Plant Sciences, vol. 165, no. 4 SUPPL., pp. S123-S135 - S123-S135, 2004.

H. H.  Hilger, ?Fruchtbiologische Untersuchungen an Heliotropioideae (Boraginaceae). I. Die Ontogenie der monospermen Früchte von Heliotropium supinum L.?, Flora, vol. 179, no. 4, pp. 291 - 303, 1987.

H. H.  Hilger, ?Flower and fruit development in the Macaronesian endemic Ceballosia fruticosa (syn. Messerschmidia fruticosa, Boraginaceae, Heliotropioideae)?, Plant Systematics and Evolution, vol. 166, no. 1, pp. 119 - 129, 1989.

H. H.  Hilger, ?Morphology of Heliotropium (Boraginaceae) dispersal units?, Botanica Acta, vol. 105, no. 5, pp. 387 - 393, 1992.

N.  Diane, Jacob, C., and Hilger, H. H., ?Leaf anatomy and foliar trichomes in Heliotropiaceae and their systematic relevance?, Flora, vol. 198, no. 6, pp. 468 - 485, 2003.

M. H.  Buys and Hilger, H. H., ?Boraginaceae cymes are exclusively scorpioid and not helicoid?, Taxon, vol. 52, no. 4, pp. 719 - 724, 2003.

F.  Luebert, Weigend, M., and Hilger, H. H., ?Epitypification of Heliotropium arborescens L. (Heliotropiaceae)?, Taxon, vol. 59, no. 4, pp. 1263 - 1266, 2010.

H. H.  Hilger and Diane, N., ?A systematic analysis of Heliotropiaceae (Boraginales) based on trnL and ITS1 sequence data?, Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie, vol. 125, pp. 19 - 51, 2003.

F.  Luebert, Brokamp, G., Wen, J., Weigend, M., and Hilger, H. H., ?Phylogenetic relationships and morphological diversity in Neotropical Heliotropium (Heliotropiaceae)?, Taxon, vol. 60, no. 3, pp. 663 - 680, 2011.

N.  Diane, Förther, H., and Hilger, H. H., ?A systematic analysis of Heliotropium, Tournefortia, and allied taxa of the Heliotropiaceae (Boraginales) based on ITS1 sequences and morphological data?, American Journal of Botany, vol. 89, no. 2, pp. 287 - 295, 2002.