20 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 52 



National Shade Tree Conference, and National Arborist Association. 

 1!)5S. Transplanting of trees and shrubs in the northeastern and 

 north central United States. Revised edition. Wooster, Ohio. 73 p. 

 [Now, National Arborist Association, Inc., 616 Southern Building, 

 Washington, D. C] 



Pirone, P. P. 1959. Tree maintenance. Third edition. Oxford Univer- 

 sity Press, New York. 483 p. 



U. S. Department of Agriculture. Agricultural Research Service, Crops 

 Research Division. 1964. Protecting trees against damage from 

 construction work. Agriculture Information Bulletin 285. 26 p. 



