@book{bhlpg5146496, title = {Botanical abstracts }, volume = {5-6. 1920-1921}, url = {https://www.biodiversitylibrary.org/page/5146496}, publisher = {Williams & Wilkins Co}, author = {Board of Control of Botanical Abstracts. }, year = {1920}, pages = {Page 173}, } @book{bhlpg37902040, title = {Fertilizer resources of the United States }, url = {https://www.biodiversitylibrary.org/page/37902040}, publisher = {[Govt. print. off.]}, author = {United States. Bureau of Soils. }, year = {1912}, pages = {Page 168}, }