Jahn, T. L. 1., & Jahn, F. F. (1949). How to know the protozoa: A pictured-key for identifying the more common fresh water, marine, and parasitic Protozoa, with elementary discussions of the importance of each group and of interesting facts concerning them. Dubuque, Iowa: Wm. C. Brown Company Publishers.

Jahn, Theodore Louis 1095-, and Frances Floed Jahn. How to Know the Protozoa: A Pictured-key for Identifying the More Common Fresh Water, Marine, and Parasitic Protozoa, With Elementary Discussions of the Importance of Each Group and of Interesting Facts Concerning Them. Dubuque, Iowa: Wm. C. Brown Company Publishers, 1949.

Jahn, Theodore Louis 1095-, and Frances Floed Jahn. How to Know the Protozoa: A Pictured-key for Identifying the More Common Fresh Water, Marine, and Parasitic Protozoa, With Elementary Discussions of the Importance of Each Group and of Interesting Facts Concerning Them. Dubuque, Iowa: Wm. C. Brown Company Publishers, 1949.