Mathiasen, R. L., and S. C. Kenaley. “Arceuthobium Tsugense (Viscaceae): Four Subspecies With Contrasting Morphologies and Host Distributions”. Journal of the Botanical Research Institute of Texas, vol. 11, no. 2, Nov. 2017, pp. 363-90, doi:10.17348/jbrit.v11.i2.1076.