The separation of Ischnoderma resinosum and I. benzoinum as distinct species is supported by morphological differences. Polyporus trogii (= Ischnoderma corrugis) is transferred to the genus Podofomes. Historical taxonomic treatments are reviewed and contrasted with the author's observations and herbarium studies.
Pouzar Z. (1971): Notes on taxonomy and nomenclature of Ischnoderma resinosum (Fr.) P. Karst. and I. benzoinum (Wahlenb.) P. Karst. (Polyporaceae). – Česká Mykologie 25(1): 15–21.