de Roon A.C. (1958). International directory of specialists in plant taxonomy: With a census of their current interests. International Bureau for Plant Taxonomy and Nomenclature..

de Roon A.C. International Directory of Specialists in Plant Taxonomy: With a Census of Their Current Interests. Utrecht, Netherlands: International Bureau for Plant Taxonomy and Nomenclature., 1958.

de Roon A.C. International Directory of Specialists in Plant Taxonomy: With a Census of Their Current Interests. International Bureau for Plant Taxonomy and Nomenclature., 1958.