Held, B. W., et al. “Occurrence of European Tar Spot (Rhytisma Acerinum) on Norway Maple (Acer Platanoides) Causing Severe Infections in Minnesota.” Plant Disease, vol. 102, no. 12, 2018, pp. 2655–2655., doi:10.1094/pdis-05-18-0816-pdn.
Hudler, George W. “Unusual Epidemic of Tar Spot on Norway Maple in Upstate New York.” Plant Disease, vol. 71, no. 1, 1987, p. 65., doi:10.1094/pd-71-0065.
“Norway Maple, Acer Platanoides Sapindales: Aceraceae.” Norway Maple, Acer Platanoides Sapindales: Aceraceae, 2018, www.invasive.org/browse/subinfo.cfm?sub=3002.
Piepenbring, M. “File:04 03 16 Life Cycle, Rhytisma Acerinum, Rhytismatales, Ascomycota (M. Piepenbring & C.-L. Hou).Png.” File:04 03 16 Life Cycle, Rhytisma Acerinum, Rhytismatales, Ascomycota (M. Piepenbring & C.-L. Hou).Png, 2015, commons.wikimedia.org/wiki/File:04_03_16_life_cycle,_Rhytisma_acerinum,_Rhytismatales,_Ascomycota_(M._Piepenbring_%26_C.-L._Hou).png#file.
“Rhytisma Acerinum.” Wikipedia, Wikimedia Foundation, 16 Nov. 2019, en.wikipedia.org/wiki/Rhytisma_acerinum.
Ulloa, Miguel, and Richard T. Hanlin. Illustrated Dictionary of Mycology. APS Press, 2012.