In 1966 he published a monograph of the genus Pinguicula, a work that is still in use today. He described at least 14 new species, most recently Pinguicula lippoldii and Pinguicula toldensis in 2007.
He published a seminal work on the Pinguicula genus in 1966, which continues to be employed today. He also made significant contributions by discovering at least 14 new species within this group, with the most recent additions being Pinguicula lippoldii and Pinguicula toldensis in 2007.