Kanigowski, P., Flakus, A., Oset, M., Kowalewska, A., Rykaczewki, M., & Kukwa, M. 2016. The lichen family Parmeliaceae in Poland. Xanthoparmelia species containing usnic acid. — Herzogia 29: 108–119.

In a study of the Xanthoparmelia species containing usnic acid in Poland, six taxa have been recognized. Xanthoparmelia plittii is new to Poland. Some of the material is referred to as X. aff. cumberlandia. Xanthoparmelia conspersa is the most common species of the group in Poland (c. 67% of all records). Xanthoparmelia angustiphylla is widespread, but less common (c. 20% of all records). The remaining Xanthoparmelia taxa in Poland, i.e. X. aff. cumberlandia, X. mougeotii, X. plittii and X. stenophylla, are rare or very rare in the country. The distribution and threat status of all taxa, their habitat requirements, morphology and secondary chemistry are discussed and notes on similar taxa are made.