1. Pinguicula mariae Casper nova spec. and Pinguicula apuana Casper et Ansaldi nova spec. — A contribution to the occurrence of the genus Pinguicula L. (Lentibulariaceae) in the Apuan Alps (Italy);Ansaldi;Wulfenia,2009
2. Taxonomic revision of the genus Pinguicula L. in the Iberian Peninsula;Blanca;Folia Geobotanica,1999
3. Monographie der Gattung Pinguicula L;Casper;Bibliotheca Botanica,1966
4. Monographie der Gattung Pinguicula L;Casper;Bibliotheca Botanica,1966