Variation of species of Sedum of the Mexican Cordilleran PlateauRobert T. Clausen · First published 1981Open the Tome
Biennial species of Sedum of the Sierra Madre Occidental and Mexican PlateauRobert T. Clausen · First published 1977Open the Tome
Najas arguta in Central America and its Relationship to N. wrightianaRobert T. Clausen · First published 1946Open the Tome
On the status of Botrychium dissectum var. oneidenseRobert T. Clausen · First published 1944Open the Tome
Northeastern limits of the known range of Rhus toxicodendrenRobert T. Clausen · First published 1941Open the Tome
