1. Berland, M. L., “L’exploration biologique del’atmos phere en avion, et l’emploi possible de cette methode enmeteorologie.” La Meteor., Ser. 3, No. 1, pp. 28–35 (1936).
2. Chester, K. S., “Airplane Spore Traps for Studying the Annual Migration of Wheat Rust.” Proc. Okla. Acad. Sci., 19: 101–104 (1939).
3. Christensen, J. J., “Long Distance Dissemination of Pathogens” in Aerobiology. (publ. by Amer. Assoc. Adv. Sci.), No. 17, pp. 78–87, 1942.
4. Committee on Apparatus in Aerobiology, Nat. Res. Comm., “Techniques for Appraising Air-Borne Populations of Microorganisms, Pollen and Insects.” Phytopathology., 31: 201–225 (1941).
5. DallaVall., J. M., and Hollaende., A., “The Effective ness of Certain Types of Commercial Air Filters against Bacteria.” Publ. Hlth. Rep., Was.., 54: 695–699 (1939).