For Campanulastrum
Crowl, A.A., E. Mavrodiev, G. Mansion, R. Haberle, A. Pistarino, G. Kamari, D. Phitos, T. Borsch, and N. Cellinese. 2014. Phylogeny of Campanuloideae (Campanulaceae) with emphasis on the utility of nuclear pentatricopeptide repeat (PPR) genes. PLOS One 9(4): e94199.
Kadereit, J.W., and C. Jeffrey. 2007. The families and genera of vascular plants. VIII. Flowering plants – Eudicots – Asterales. Springer, Berlin. 636 pp.
Mansion, G., G. Parolly, A.A. Crowl, E. Mavrodiev, N. Cellinese, M. Oganesian, K. Fraunhofer, G. Kamari, D. Phitos, R. Haberle, G. Akaydin, N. Ikinci, T. Raus, and T. Borsch. 2012. How to handle speciose clades? Mass taxon-sampling as a strategy towards illuminating the natural history of Campanula (Campanuloideae. PLOS ONE 7: e50076.
Morin, N.R. 2020. Taxonomic changes in North American Campanuloideae (Campanulaceae). Phytoneuron 2020-49: 1-46. Published 15 July 2020. ISSN 2153 733X
Roquet, C., S.G. Llorenç, J.J. Aldasoro, A. Susanna, M.L. Alarcón, and N. Garcia-Jacas. 2008. Natural delineation, molecular phylogeny and floral evolution in Campanula. Systematic Bot. 33: 203-217.
Rosatti, T.J. 1986. The genera of Sphenocleaceae and Campanulaceae in the southeastern United States. J. Arnold Arb. 67: 1-64.
Shetler, S.G., and N.R. Morin. 1986. Seed morphology in North American Campanulaceae. Ann. Mo. Bot. Gard. 73: 653-688.
Shulkina, T.V., J.F. Gaskin, and W.M.M. Eddie. 2003. Morphological studies toward an improved classification of Campanulaceae s. str. Ann. Missouri Bot. Gard. 90: 576-591.