Per Axel Rydberg

• Flora of the Black Hills of South Dakota
• Flora of the Sand Hills of Nebraska
• Flora of the prairies and plains of central North America,
• Flora of the Rocky Mountains and adjacent plains
• Key to the Rocky Mountain Flora
• Report upon the Grasses and Forage Plants of the Rocky Mountain Region, Volumes 1-10
• Rydberg Flora Prairies V2
• Scandinavians Who Have Contributed to the Knowledge of the Flora of North America, Volume 1907, Part 1